Re: [libvirt] [PATCH 1/3] virNumaGetPageInfo: Take huge pages into account

On the Linux kernel, if huge pages are allocated the size they cut off from memory is accounted under the 'MemUsed' in the meminfo file. However, we want the sum to be subtracted from 'MemTotal'. This patch implements this feature. After this change, we can enable reporting of the ordinary system pages in the capability XML: <capabilities> <host> <uuid>01281cda-f352-cb11-a9db-e905fe22010c</uuid> <cpu> <arch>x86_64</arch> <model>Haswell</model> <vendor>Intel</vendor> <topology sockets='1' cores='1' threads='1'/> <feature/> <pages unit='KiB' size='4'/> <pages unit='KiB' size='2048'/> <pages unit='KiB' size='1048576'/> </cpu> <power_management/> <migration_features/> <topology> <cells num='4'> <cell id='0'> <memory unit='KiB'>4048248</memory> <pages unit='KiB' size='4'>748382</pages> <pages unit='KiB' size='2048'>3</pages> <pages unit='KiB' size='1048576'>1</pages> <distances/> <cpus num='1'> <cpu id='0' socket_id='0' core_id='0' siblings='0'/> </cpus> </cell> ... </cells> </topology> </host> </capabilities> You can see the beautiful thing about this: if you sum up all the <pages/> you'll get <memory/>. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/nodeinfo.c | 2 +- src/util/virnuma.c | 65 +++++++++++++++++++++++++++++++----------------------- src/util/virnuma.h | 1 + 3 files changed, 39 insertions(+), 29 deletions(-)

@@ -647,6 +649,13 @@ virNumaGetHugePageInfo(int node, * total number of pages in the pool (both free and taken) * and count for free pages in the pool. * + * The @huge_page_sum parameter exists there due to the Linux

+ * kernel limitation. The problem is, if there are some huge + * pages allocated, they are accounted under the 'MemUsed' field + * in the meminfo file instead of being subtracted from the + * 'MemTotal'. We must do the subtraction ourselves. + * If unsure, pass 0. + * * If you're interested in just one bit, pass NULL to the other one. * * As a special case, if @node == -1, overall info is fetched @@ -657,6 +666,7 @@ virNumaGetHugePageInfo(int node, int virNumaGetPageInfo(int node, unsigned int page_size, + unsigned long long huge_page_sum, unsigned int *page_avail, unsigned int *page_free) { @@ -666,7 +676,6 @@ virNumaGetPageInfo(int node, /* sysconf() returns page size in bytes, * the @page_size is however in kibibytes */ if (page_size == system_page_size / 1024) { -# if 0 unsigned long long memsize, memfree; /* TODO: come up with better algorithm that takes huge pages into @@ -679,16 +688,14 @@ virNumaGetPageInfo(int node, goto cleanup; } + /* see description above */

+ memsize -= huge_page_sum; + if (page_avail) *page_avail = memsize / system_page_size; if (page_free) *page_free = memfree / system_page_size;