Alex Williams
2010-Apr-15 15:54 UTC
[Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
Hello, I noticed a significant *decrease* (150MB) in "total_memory" on a host build using XEN 4.0.0 with kernel 2.6.18. Here are the details: Server = 4096MB RAM XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 The exact same kernel config file was used for both builds. I also made sure there is absolutely no difference on the hosts (while the builds are created on a different machine). This seems like a regression, unless someone can provide suggestions on how to correct this? Thanks. -- Alexander Williams IT Architecture Specialist Spécialiste de l''Architecture TI http://www.iWeb.com/ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-Apr-15 16:33 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
Are the hypervisor and dom0 kernel 64-bit or 32-bit? Xen prints a message "System RAM: xxx" early during boot. Do these differ significantly for you between 3.4.2 and 4.0.0? K. On 15/04/2010 16:54, "Alex Williams" <awilliams@iweb.com> wrote:> Hello, > > I noticed a significant *decrease* (150MB) in "total_memory" on a host > build using XEN 4.0.0 with kernel 2.6.18. > > Here are the details: > > Server = 4096MB RAM > XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 > XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 > > The exact same kernel config file was used for both builds. I also made > sure there is absolutely no difference on the hosts (while the builds > are created on a different machine). > > This seems like a regression, unless someone can provide suggestions on > how to correct this? > > Thanks. >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Alex Williams
2010-Apr-15 17:33 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
Hello, Both builds run a 64-bit Xen kernel and 64-bit Dom0 kernel. (XEN) Xen kernel: 64-bit, lsb, compat32 (XEN) Dom0 kernel: 64-bit, lsb, paddr 0xffffffff80200000 -> 0xffffffff805d388c As for the RAM: Xen 3.4.2: (XEN) System RAM: 3946MB (4041012kB) Xen 4.0.0: (XEN) System RAM: 4084MB (4182064kB) I have also verified with only 2048MB installed in the system. Here are the results: Xen 3.4.2: (XEN) System RAM: 2036MB (2084912kB) Xen 4.0.0: (XEN) System RAM: 1898MB (1943860kB) Still 150MB RAM missing... it appears this problem is static and independant of the amount of RAM installed in the system. Regards, Keir Fraser wrote:> Are the hypervisor and dom0 kernel 64-bit or 32-bit? Xen prints a message > "System RAM: xxx" early during boot. Do these differ significantly for you > between 3.4.2 and 4.0.0? > > K. > > On 15/04/2010 16:54, "Alex Williams" <awilliams@iweb.com> wrote: > >> Hello, >> >> I noticed a significant *decrease* (150MB) in "total_memory" on a host >> build using XEN 4.0.0 with kernel 2.6.18. >> >> Here are the details: >> >> Server = 4096MB RAM >> XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 >> XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 >> >> The exact same kernel config file was used for both builds. I also made >> sure there is absolutely no difference on the hosts (while the builds >> are created on a different machine). >> >> This seems like a regression, unless someone can provide suggestions on >> how to correct this? >> >> Thanks. >> > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel >-- Alexander Williams IT Architecture Specialist Spécialiste de l''Architecture TI http://www.iWeb.com/ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Alex Williams
2010-Apr-15 17:42 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
Hi, I also want to add, my build process is practically automated. The only difference I had to make for 4.0.0 was: - Install Debian package dependencies: uuid-dev iasl gcc-multilib Let me know if you need more information. Thanks. Alex Williams wrote:> Hello, > > Both builds run a 64-bit Xen kernel and 64-bit Dom0 kernel. > > (XEN) Xen kernel: 64-bit, lsb, compat32 > (XEN) Dom0 kernel: 64-bit, lsb, paddr 0xffffffff80200000 -> > 0xffffffff805d388c > > As for the RAM: > > Xen 3.4.2: (XEN) System RAM: 3946MB (4041012kB) > Xen 4.0.0: (XEN) System RAM: 4084MB (4182064kB) > > I have also verified with only 2048MB installed in the system. Here are > the results: > > Xen 3.4.2: (XEN) System RAM: 2036MB (2084912kB) > Xen 4.0.0: (XEN) System RAM: 1898MB (1943860kB) > > Still 150MB RAM missing... it appears this problem is static and > independant of the amount of RAM installed in the system. > > Regards, > > > > Keir Fraser wrote: >> Are the hypervisor and dom0 kernel 64-bit or 32-bit? Xen prints a message >> "System RAM: xxx" early during boot. Do these differ significantly for >> you >> between 3.4.2 and 4.0.0? >> >> K. >> >> On 15/04/2010 16:54, "Alex Williams" <awilliams@iweb.com> wrote: >> >>> Hello, >>> >>> I noticed a significant *decrease* (150MB) in "total_memory" on a host >>> build using XEN 4.0.0 with kernel 2.6.18. >>> >>> Here are the details: >>> >>> Server = 4096MB RAM >>> XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 >>> XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 >>> >>> The exact same kernel config file was used for both builds. I also made >>> sure there is absolutely no difference on the hosts (while the builds >>> are created on a different machine). >>> >>> This seems like a regression, unless someone can provide suggestions on >>> how to correct this? >>> >>> Thanks. >>> >> >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> >-- Alexander Williams IT Architecture Specialist Spécialiste de l''Architecture TI http://www.iWeb.com/ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-Apr-15 18:05 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
Ah, hm, I think this is a bug in total memory reporting only. I think the memory is still there in the free pools though. :-) How does xm info''s free_memory compare in the two cases? I bet it''s a lot closer than 150MB (assuming dom0 is allocated the same amount of memory in both cases, e.g., by explicitly specifying dom0_mem=xxx on Xen command line). -- Keir On 15/04/2010 18:33, "Alex Williams" <awilliams@iweb.com> wrote:> Hello, > > Both builds run a 64-bit Xen kernel and 64-bit Dom0 kernel. > > (XEN) Xen kernel: 64-bit, lsb, compat32 > (XEN) Dom0 kernel: 64-bit, lsb, paddr 0xffffffff80200000 -> > 0xffffffff805d388c > > As for the RAM: > > Xen 3.4.2: (XEN) System RAM: 3946MB (4041012kB) > Xen 4.0.0: (XEN) System RAM: 4084MB (4182064kB) > > I have also verified with only 2048MB installed in the system. Here are > the results: > > Xen 3.4.2: (XEN) System RAM: 2036MB (2084912kB) > Xen 4.0.0: (XEN) System RAM: 1898MB (1943860kB) > > Still 150MB RAM missing... it appears this problem is static and > independant of the amount of RAM installed in the system. > > Regards, > > > > Keir Fraser wrote: >> Are the hypervisor and dom0 kernel 64-bit or 32-bit? Xen prints a message >> "System RAM: xxx" early during boot. Do these differ significantly for you >> between 3.4.2 and 4.0.0? >> >> K. >> >> On 15/04/2010 16:54, "Alex Williams" <awilliams@iweb.com> wrote: >> >>> Hello, >>> >>> I noticed a significant *decrease* (150MB) in "total_memory" on a host >>> build using XEN 4.0.0 with kernel 2.6.18. >>> >>> Here are the details: >>> >>> Server = 4096MB RAM >>> XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 >>> XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 >>> >>> The exact same kernel config file was used for both builds. I also made >>> sure there is absolutely no difference on the hosts (while the builds >>> are created on a different machine). >>> >>> This seems like a regression, unless someone can provide suggestions on >>> how to correct this? >>> >>> Thanks. >>> >> >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >>_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-Apr-15 18:23 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
I''ve fixed this regression as xen-unstable:21190 and xen-4.0-testing:21114. The fix will appear in Xen 4.0.1. Thanks, Keir On 15/04/2010 19:05, "Keir Fraser" <keir.fraser@eu.citrix.com> wrote:> Ah, hm, I think this is a bug in total memory reporting only. I think the > memory is still there in the free pools though. :-) How does xm info''s > free_memory compare in the two cases? I bet it''s a lot closer than 150MB > (assuming dom0 is allocated the same amount of memory in both cases, e.g., > by explicitly specifying dom0_mem=xxx on Xen command line). > > -- Keir > > On 15/04/2010 18:33, "Alex Williams" <awilliams@iweb.com> wrote: > >> Hello, >> >> Both builds run a 64-bit Xen kernel and 64-bit Dom0 kernel. >> >> (XEN) Xen kernel: 64-bit, lsb, compat32 >> (XEN) Dom0 kernel: 64-bit, lsb, paddr 0xffffffff80200000 -> >> 0xffffffff805d388c >> >> As for the RAM: >> >> Xen 3.4.2: (XEN) System RAM: 3946MB (4041012kB) >> Xen 4.0.0: (XEN) System RAM: 4084MB (4182064kB) >> >> I have also verified with only 2048MB installed in the system. Here are >> the results: >> >> Xen 3.4.2: (XEN) System RAM: 2036MB (2084912kB) >> Xen 4.0.0: (XEN) System RAM: 1898MB (1943860kB) >> >> Still 150MB RAM missing... it appears this problem is static and >> independant of the amount of RAM installed in the system. >> >> Regards, >> >> >> >> Keir Fraser wrote: >>> Are the hypervisor and dom0 kernel 64-bit or 32-bit? Xen prints a message >>> "System RAM: xxx" early during boot. Do these differ significantly for you >>> between 3.4.2 and 4.0.0? >>> >>> K. >>> >>> On 15/04/2010 16:54, "Alex Williams" <awilliams@iweb.com> wrote: >>> >>>> Hello, >>>> >>>> I noticed a significant *decrease* (150MB) in "total_memory" on a host >>>> build using XEN 4.0.0 with kernel 2.6.18. >>>> >>>> Here are the details: >>>> >>>> Server = 4096MB RAM >>>> XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 >>>> XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 >>>> >>>> The exact same kernel config file was used for both builds. I also made >>>> sure there is absolutely no difference on the hosts (while the builds >>>> are created on a different machine). >>>> >>>> This seems like a regression, unless someone can provide suggestions on >>>> how to correct this? >>>> >>>> Thanks. >>>> >>> >>> >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >>> > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Alex Williams
2010-Apr-15 18:26 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
Yes you''re correct! Both hosts have dom0_mem=512M set. Xen 3.4.2: free_memory : 3514 Xen 4.0.0: free_memory : 3523 So now it appears to be a free memory INCREASE caused by this ''bug'' ? ;) Thank you!!! Keir Fraser wrote:> Ah, hm, I think this is a bug in total memory reporting only. I think the > memory is still there in the free pools though. :-) How does xm info''s > free_memory compare in the two cases? I bet it''s a lot closer than 150MB > (assuming dom0 is allocated the same amount of memory in both cases, e.g., > by explicitly specifying dom0_mem=xxx on Xen command line). > > -- Keir > > On 15/04/2010 18:33, "Alex Williams" <awilliams@iweb.com> wrote: > >> Hello, >> >> Both builds run a 64-bit Xen kernel and 64-bit Dom0 kernel. >> >> (XEN) Xen kernel: 64-bit, lsb, compat32 >> (XEN) Dom0 kernel: 64-bit, lsb, paddr 0xffffffff80200000 -> >> 0xffffffff805d388c >> >> As for the RAM: >> >> Xen 3.4.2: (XEN) System RAM: 3946MB (4041012kB) >> Xen 4.0.0: (XEN) System RAM: 4084MB (4182064kB) >> >> I have also verified with only 2048MB installed in the system. Here are >> the results: >> >> Xen 3.4.2: (XEN) System RAM: 2036MB (2084912kB) >> Xen 4.0.0: (XEN) System RAM: 1898MB (1943860kB) >> >> Still 150MB RAM missing... it appears this problem is static and >> independant of the amount of RAM installed in the system. >> >> Regards, >> >> >> >> Keir Fraser wrote: >>> Are the hypervisor and dom0 kernel 64-bit or 32-bit? Xen prints a message >>> "System RAM: xxx" early during boot. Do these differ significantly for you >>> between 3.4.2 and 4.0.0? >>> >>> K. >>> >>> On 15/04/2010 16:54, "Alex Williams" <awilliams@iweb.com> wrote: >>> >>>> Hello, >>>> >>>> I noticed a significant *decrease* (150MB) in "total_memory" on a host >>>> build using XEN 4.0.0 with kernel 2.6.18. >>>> >>>> Here are the details: >>>> >>>> Server = 4096MB RAM >>>> XEN 3.4.2 + kernel 2.6.18: xm info | grep total_memory = 4084 >>>> XEN 4.0.0 + kernel 2.6.18: xm info | grep total_memory = 3946 >>>> >>>> The exact same kernel config file was used for both builds. I also made >>>> sure there is absolutely no difference on the hosts (while the builds >>>> are created on a different machine). >>>> >>>> This seems like a regression, unless someone can provide suggestions on >>>> how to correct this? >>>> >>>> Thanks. >>>>-- Alexander Williams IT Architecture Specialist Spécialiste de l''Architecture TI http://www.iWeb.com/ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-Apr-15 18:34 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
On 15/04/2010 19:26, "Alex Williams" <awilliams@iweb.com> wrote:> Yes you''re correct! Both hosts have dom0_mem=512M set. > > Xen 3.4.2: free_memory : 3514 > Xen 4.0.0: free_memory : 3523 > > So now it appears to be a free memory INCREASE caused by this ''bug'' ? ;)The reason for the increase is that for various technical reasons we used to carve off 16MB of memory into a separate memory allocator used for Xen''s own internal book-keeping structures. We no longer have that and so that 16MB is now part of the ordinary allocation pool. So you see 9MB extra in that pool, which is that 16MB minus the book-keeping allocations (about 7MB of them) which now occur from the unified pool. -- Keir> Thank you!!!_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Jan Beulich
2010-Apr-16 07:53 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
>>> Keir Fraser <keir.fraser@eu.citrix.com> 15.04.10 20:23 >>> >I''ve fixed this regression as xen-unstable:21190 and xen-4.0-testing:21114. >The fix will appear in Xen 4.0.1.That seems wrong to me - I specifically changed the accounting so that pieces not used from the E820 map (which can no longer be cut off in e820.c, as that code doesn''t know *where* to cut off) won''t get reported as available memory. The real question is where (for the non-cut-off case) the two calculations differ. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-Apr-16 17:37 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
On 16/04/2010 08:53, "Jan Beulich" <JBeulich@novell.com> wrote:>>>> Keir Fraser <keir.fraser@eu.citrix.com> 15.04.10 20:23 >>> >> I''ve fixed this regression as xen-unstable:21190 and xen-4.0-testing:21114. >> The fix will appear in Xen 4.0.1. > > That seems wrong to me - I specifically changed the accounting so > that pieces not used from the E820 map (which can no longer be cut > off in e820.c, as that code doesn''t know *where* to cut off) won''t > get reported as available memory. The real question is where (for > the non-cut-off case) the two calculations differ.boot_e820 has chunks cut out of it for stashing kexec stuff, as well as all the multiboot modules. The value thereby obtained is just confusing to users who think we''ve binned possibly 100s of megabytes (if they run a big initrd). -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Jan Beulich
2010-Apr-19 07:35 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
>>> Keir Fraser <keir.fraser@eu.citrix.com> 16.04.10 19:37 >>> >On 16/04/2010 08:53, "Jan Beulich" <JBeulich@novell.com> wrote: > >>>>> Keir Fraser <keir.fraser@eu.citrix.com> 15.04.10 20:23 >>> >>> I''ve fixed this regression as xen-unstable:21190 and xen-4.0-testing:21114. >>> The fix will appear in Xen 4.0.1. >> >> That seems wrong to me - I specifically changed the accounting so >> that pieces not used from the E820 map (which can no longer be cut >> off in e820.c, as that code doesn''t know *where* to cut off) won''t >> get reported as available memory. The real question is where (for >> the non-cut-off case) the two calculations differ. > >boot_e820 has chunks cut out of it for stashing kexec stuff, as well as all >the multiboot modules. The value thereby obtained is just confusing to users >who think we''ve binned possibly 100s of megabytes (if they run a big >initrd).The piece cut off for kexec imo shouldn''t be counted as (usable) system RAM; the piece for the multiboot modules certainly should, but perhaps it would then be better to account for that explicitly instead of reporting a possibly much higher value than is actually available at runtime? Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2010-Apr-19 07:51 UTC
Re: [Xen-devel] Possible regression: XEN 4.0.0 total_memory decrease
On 19/04/2010 08:35, "Jan Beulich" <JBeulich@novell.com> wrote:>> boot_e820 has chunks cut out of it for stashing kexec stuff, as well as all >> the multiboot modules. The value thereby obtained is just confusing to users >> who think we''ve binned possibly 100s of megabytes (if they run a big >> initrd). > > The piece cut off for kexec imo shouldn''t be counted as (usable) > system RAM; the piece for the multiboot modules certainly should, > but perhaps it would then be better to account for that explicitly > instead of reporting a possibly much higher value than is actually > available at runtime?I think it''s quite open to debate what should be included in total_memory. Certainly I think kexec can be, as why is it different from any other in-use memory in the system in that regard? -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel