> 1 GB RAM on a 32-bit system

By: Tzvetan Mikov (tzvetanmi.delete@this.yahoo.com), May 13, 2007 5:23 pm
Room: Moderated Discussions
Linus Torvalds on 5/13/07 wrote:
---------------------------
>[...]
>>So, in practical terms, is there benefit from using
>>64-bit OS on a machine with, lets say, 2-3 GB RAM ?
>
>Absolutely. No question what-so-ever. If you have 2GB
>of RAM on a 64-bit architecture, you can access it all
>easily in the kernel, and none of it is limited to just
>some special use. And a single big process can also use
>it effectively at the same time, so a database can
>actually have it all mapped without having to play
>windowing games in user space either.

Thanks. This was very informative. I guess I didn't actually realize that the HIGHMEM limit is not 4GB but 1GB-128MB (I guess depending on VMSPLIT_xx).

It appears that as far as kernel complexity is concerned, PAE (CONFIG_HIGHMEM64G) is not that much worse than simply having to support >1GB RAM (CONFIG_HIGHMEM4G).

If anybody is interested in some more details, I found this high level overview:
http://kerneltrap.org/node/2450

Mel Gorman's book "Understanding The Linux Virtual Memory Manager" covers it in some more detail. It is available online here:
http://www.phptr.com/content/images/0131453483/downloads/gorman_book.pdf

It seems the complication is already there and isn't ever going away. All driver code that needs to use the CPU to access process memory outside of the current process context needs to use kmap()/kunmap(), even though on a 64-bit system they don't do anything.

regards,
Tzvetan
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Rock/Tukwila rumorsmas05/05/07 12:59 PM
  Rock/Tukwila rumorsDavid Kanter05/05/07 02:33 PM
    Rock/Tukwila rumorsDean Kent05/05/07 03:35 PM
      K8 vs Win64 timelineanonymous05/05/07 06:19 PM
        Yes, I misremembered...Dean Kent05/05/07 10:03 PM
    RockDaniel Biz√≥05/06/07 02:34 AM
      RockDean Kent05/06/07 07:11 AM
    Rock/Tukwila rumorsJoe05/06/07 11:24 AM
      Rock/Tukwila rumorsDean Kent05/06/07 11:49 AM
      Rock/Tukwila rumorsLinus Torvalds05/06/07 12:09 PM
      Rock/Tukwila rumorsanon05/07/07 01:32 AM
        Rock/Tukwila rumorsRakesh Malik05/07/07 09:36 AM
          Rock/Tukwila rumorsMichael S05/07/07 10:06 AM
          Rock/Tukwila rumorsanon05/07/07 09:48 PM
            Rock/Tukwila rumorsRakesh Malik05/08/07 06:45 AM
              Rock/Tukwila rumorsanon05/08/07 05:30 PM
                Wow. (nt)Brannon05/08/07 06:16 PM
                Rock/Tukwila rumorsrwessel05/08/07 09:48 PM
                  Rock/Tukwila rumorsJS05/08/07 10:07 PM
                    Rock/Tukwila rumorsJS05/09/07 06:44 AM
                Rock/Tukwila rumorsRakesh Malik05/09/07 05:35 AM
                  Much ado about xMichael S05/09/07 09:39 AM
                    Call it x86-64Linus Torvalds05/09/07 10:27 AM
                      (i)AMD64Michael S05/09/07 12:16 PM
                        (i)AMD64Linus Torvalds05/09/07 12:29 PM
                          (i)AMD64Groo05/09/07 04:45 PM
                          TIFNAAanonymous05/09/07 05:49 PM
                            Inspired by FYR Macedonia? (NT)Michael S05/09/07 11:21 PM
                              More likely...rwessel05/10/07 12:39 AM
                            TIFNAAGabriele Svelto05/09/07 11:57 PM
                          (i)AMD64James05/10/07 02:27 AM
                        i86Dean Kent05/09/07 12:30 PM
                        (i)AMD64Max05/09/07 01:28 PM
                          wide86? long86?hobold05/10/07 05:05 AM
                            x87 perhaps, it is one more. :) (NT)Groo05/10/07 05:50 AM
                              x86+Dean Kent05/10/07 08:44 AM
                                Does it really matter?Doug Siebert05/10/07 09:10 AM
                                  let's stay with x86-64 for now, pleaseMarcin Niewiadomski05/10/07 11:50 AM
                                    let's stay with x86-64 for now, pleaseDean Kent05/11/07 06:11 AM
                                      let's stay with x86-64 for now, pleaserwessel05/11/07 02:46 PM
                                        let's stay with x86-64 for now, pleaseDean Kent05/11/07 06:03 PM
                                          let's stay with x86-64 for now, pleaseMichael S05/12/07 10:49 AM
                                            let's stay with x86-64 for now, pleaseDean Kent05/12/07 01:05 PM
                                              let's stay with x86-64 for now, pleaseMichael S05/12/07 01:25 PM
                                                let's stay with x86-64 for now, pleaseDean Kent05/12/07 03:39 PM
                                                  let's stay with x86-64 for now, pleaseJasonB05/13/07 07:43 AM
                                                    client consolidationMichael S05/13/07 08:37 AM
                                                  let's stay with x86-64 for now, pleaseTzvetan Mikov05/13/07 03:44 PM
                                                let's stay with x86-64 for now, pleaserwessel05/14/07 02:42 PM
                                      What's your point?Doug Siebert05/11/07 02:56 PM
                                        What's your point?Linus Torvalds05/11/07 04:15 PM
                                          What's your point?Doug Siebert05/13/07 03:11 PM
                                            What's your point?Dean Kent05/13/07 07:04 PM
                                              What's your point?JasonB05/14/07 02:06 AM
                                                What's your point?Dean Kent05/14/07 07:20 AM
                                                  What's your point?JasonB05/14/07 04:35 PM
                                                  What's your point?JasonB05/14/07 07:35 PM
                                                    What's your point?Dean Kent05/14/07 08:12 PM
                                        What's your point?Dean Kent05/11/07 06:06 PM
                                        What's your point?Stephen H05/13/07 01:55 AM
                                          Why didn't MS take advantage of PAE?David W. Hess05/13/07 08:37 AM
                                            PAE sucks (Why didn't MS take advantage of PAE?)Linus Torvalds05/13/07 10:20 AM
                                              PAE sucks (Why didn't MS take advantage of PAE?)Dean Kent05/13/07 10:49 AM
                                              PAE sucks (Why didn't MS take advantage of PAE?)David W. Hess05/13/07 12:37 PM
                                              > 1 GB RAM on a 32-bit systemTzvetan Mikov05/13/07 01:44 PM
                                                > 1 GB RAM on a 32-bit systemS. Rao05/13/07 03:00 PM
                                                  > 1 GB RAM on a 32-bit systemTzvetan Mikov05/13/07 05:32 PM
                                                    > 1 GB RAM on a 32-bit systemS. Rao05/14/07 12:19 AM
                                                > 1 GB RAM on a 32-bit systemLinus Torvalds05/13/07 03:46 PM
                                                  > 1 GB RAM on a 32-bit systemTzvetan Mikov05/13/07 05:23 PM
                                                  > 1 GB RAM on a 32-bit systemJasonB05/13/07 06:37 PM
                                                    Windows manages memory differentlyTzvetan Mikov05/13/07 08:31 PM
                                                      Windows manages memory differentlyJasonB05/14/07 01:50 AM
                                                        Windows manages memory differentlyTzvetan Mikov05/14/07 08:56 AM
                                                          Windows manages memory differentlyrwessel05/14/07 03:40 PM
                                                            Windows manages memory differentlyDavid W. Hess05/14/07 04:07 PM
                                                              Windows manages memory differentlyrwessel05/14/07 04:51 PM
                                                            Windows manages memory differentlyTzvetan Mikov05/14/07 05:40 PM
                                                              Windows manages memory differentlyrwessel05/14/07 06:09 PM
                                                      Windows manages memory differentlyHoward Chu05/14/07 11:17 AM
                                                        Windows manages memory differentlyJukka Larja05/14/07 11:30 AM
                                                        Windows manages memory differentlyTzvetan Mikov05/14/07 01:54 PM
                                                          Windows manages memory differentlyHoward Chu05/15/07 03:35 AM
                                                            Windows manages memory differentlyGroo05/15/07 07:34 AM
                                                      Anyone know what OS X (10.4, Intel, desktop) does?Matt Sayler05/15/07 06:23 AM
                                                        Anyone know what OS X (10.4, Intel, desktop) does?Wes Felter05/15/07 08:37 AM
                                                        Anyone know what OS X (10.4, Intel, desktop) does?Anonymous05/15/07 10:49 AM
                                                        Anyone know what OS X (10.4, Intel, desktop) does?anon205/15/07 07:13 PM
                                              PAE sucks (Why didn't MS take advantage of PAE?)Paul05/13/07 03:40 PM
                                                PAE sucks (Why didn't MS take advantage of PAE?)Peter Arremann05/13/07 05:38 PM
                                                  PAE sucks (Why didn't MS take advantage of PAE?)Henrik S05/14/07 03:31 AM
                                              The fragility of your argumentslacker05/13/07 03:56 PM
                                                The fragility of your argumentnick05/13/07 05:42 PM
                                                The fragility of your argumentHoward Chu05/14/07 02:52 AM
                                                  The fragility of your argumentDean Kent05/14/07 09:19 AM
                                                The fragility of your argumentanon205/14/07 08:26 AM
                                                  The fragility of your argumentTzvetan Mikov05/14/07 09:01 AM
                                                  The fragility of your argumentDean Kent05/14/07 09:16 AM
                                                    The fragility of your argumentLinus Torvalds05/14/07 11:57 AM
                                                      The fragility of your argumentJasonB05/14/07 04:48 PM
                                                        The fragility of your argumentDean Kent05/14/07 07:36 PM
                                                          The fragility of your argumentRicardo B05/16/07 02:40 AM
                                                            The fragility of your argumentDean Kent05/16/07 03:32 AM
                                                              The fragility of your argumentRicardo B05/16/07 06:41 AM
                                                                PSRicardo B05/16/07 06:50 AM
                                                                The fragility of your argumentDean Kent05/16/07 09:07 AM
                                                                  Modern web browsingS. Rao05/16/07 09:16 AM
                                                                    Aha!Dean Kent05/16/07 09:27 AM
                                                                      Aha!Dean Kent05/16/07 09:32 AM
                                                                        Aha!S. Rao05/16/07 10:34 AM
                                                                  The fragility of your argumentRicardo B05/16/07 10:00 AM
                                                      The fragility of your argumentVincent Diepeveen05/16/07 10:10 AM
                                                        The fragility of your argumentPaul05/16/07 03:01 PM
                                                          The fragility of your argumentVincent Diepeveen05/17/07 03:05 AM
                                                    The fragility of your argumentanon205/15/07 01:35 AM
                                                    Splits vs page allocations?Matt Sayler05/15/07 07:33 AM
                                          What's your point?Michael S05/13/07 08:55 AM
                                            What's your point?anonymous05/13/07 11:08 AM
                                              What's your point?Michael S05/13/07 11:31 AM
                                      let's stay with x86-64 for now, pleaseJasonB05/13/07 07:16 AM
                                x864 =) (NT)some105/15/07 03:03 AM
    Rock/Tukwila rumorsIntelUser200005/06/07 02:27 PM
  Rock/Tukwila rumorsm05/13/07 08:05 AM
  Rock/Tukwila rumorsmas05/15/07 09:40 AM
Reply to this Topic
Name:
Email:
Topic:
Body: No Text
How do you spell green?