From: Mina Almasry <almasrymina@google.com> To: mike.kravetz@oracle.com Cc: shuah@kernel.org, almasrymina@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, Hillf Danton <hdanton@sina.com> Subject: [PATCH v8 9/9] hugetlb_cgroup: Add hugetlb_cgroup reservation docs Date: Tue, 29 Oct 2019 18:37:01 -0700 [thread overview] Message-ID: <20191030013701.39647-9-almasrymina@google.com> (raw) In-Reply-To: <20191030013701.39647-1-almasrymina@google.com> Add docs for how to use hugetlb_cgroup reservations, and their behavior. Signed-off-by: Mina Almasry <almasrymina@google.com> Acked-by: Hillf Danton <hdanton@sina.com> --- Changes in v6: - Updated docs to reflect the new design based on a new counter that tracks both reservations and faults. --- .../admin-guide/cgroup-v1/hugetlb.rst | 64 +++++++++++++++---- 1 file changed, 53 insertions(+), 11 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentation/admin-guide/cgroup-v1/hugetlb.rst index a3902aa253a96..efb94e4db9d5a 100644 --- a/Documentation/admin-guide/cgroup-v1/hugetlb.rst +++ b/Documentation/admin-guide/cgroup-v1/hugetlb.rst @@ -2,13 +2,6 @@ HugeTLB Controller ================== -The HugeTLB controller allows to limit the HugeTLB usage per control group and -enforces the controller limit during page fault. Since HugeTLB doesn't -support page reclaim, enforcing the limit at page fault time implies that, -the application will get SIGBUS signal if it tries to access HugeTLB pages -beyond its limit. This requires the application to know beforehand how much -HugeTLB pages it would require for its use. - HugeTLB controller can be created by first mounting the cgroup filesystem. # mount -t cgroup -o hugetlb none /sys/fs/cgroup @@ -28,10 +21,14 @@ process (bash) into it. Brief summary of control files:: - hugetlb.<hugepagesize>.limit_in_bytes # set/show limit of "hugepagesize" hugetlb usage - hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded - hugetlb.<hugepagesize>.usage_in_bytes # show current usage for "hugepagesize" hugetlb - hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB limit + hugetlb.<hugepagesize>.reservation_limit_in_bytes # set/show limit of "hugepagesize" hugetlb reservations + hugetlb.<hugepagesize>.reservation_max_usage_in_bytes # show max "hugepagesize" hugetlb reservations and no-reserve faults. + hugetlb.<hugepagesize>.reservation_usage_in_bytes # show current reservations and no-reserve faults for "hugepagesize" hugetlb + hugetlb.<hugepagesize>.reservation_failcnt # show the number of allocation failure due to HugeTLB reservation limit + hugetlb.<hugepagesize>.limit_in_bytes # set/show limit of "hugepagesize" hugetlb faults + hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded + hugetlb.<hugepagesize>.usage_in_bytes # show current usage for "hugepagesize" hugetlb + hugetlb.<hugepagesize>.failcnt # show the number of allocation failure due to HugeTLB usage limit For a system supporting three hugepage sizes (64k, 32M and 1G), the control files include:: @@ -40,11 +37,56 @@ files include:: hugetlb.1GB.max_usage_in_bytes hugetlb.1GB.usage_in_bytes hugetlb.1GB.failcnt + hugetlb.1GB.reservation_limit_in_bytes + hugetlb.1GB.reservation_max_usage_in_bytes + hugetlb.1GB.reservation_usage_in_bytes + hugetlb.1GB.reservation_failcnt hugetlb.64KB.limit_in_bytes hugetlb.64KB.max_usage_in_bytes hugetlb.64KB.usage_in_bytes hugetlb.64KB.failcnt + hugetlb.64KB.reservation_limit_in_bytes + hugetlb.64KB.reservation_max_usage_in_bytes + hugetlb.64KB.reservation_usage_in_bytes + hugetlb.64KB.reservation_failcnt hugetlb.32MB.limit_in_bytes hugetlb.32MB.max_usage_in_bytes hugetlb.32MB.usage_in_bytes hugetlb.32MB.failcnt + hugetlb.32MB.reservation_limit_in_bytes + hugetlb.32MB.reservation_max_usage_in_bytes + hugetlb.32MB.reservation_usage_in_bytes + hugetlb.32MB.reservation_failcnt + + +1. Reservation limits + +The HugeTLB controller allows to limit the HugeTLB reservations per control +group and enforces the controller limit at reservation time and at the fault of +hugetlb memory for which no reservation exists. Reservation limits +are superior to Page fault limits (see section 2), since Reservation limits are +enforced at reservation time (on mmap or shget), and never causes the +application to get SIGBUS signal if the memory was reserved before hand. For +MAP_NORESERVE allocations, the reservation limit behaves the same as the fault +limit, enforcing memory usage at fault time and causing the application to +receive a SIGBUS if it's crossing its limit. + +2. Page fault limits + +The HugeTLB controller allows to limit the HugeTLB usage (page fault) per +control group and enforces the controller limit during page fault. Since HugeTLB +doesn't support page reclaim, enforcing the limit at page fault time implies +that, the application will get SIGBUS signal if it tries to access HugeTLB +pages beyond its limit. This requires the application to know beforehand how +much HugeTLB pages it would require for its use. + + +3. Caveats with shared memory + +For shared hugetlb memory, both hugetlb reservation and page faults are charged +to the first task that causes the memory to be reserved or faulted, and all +subsequent uses of this reserved or faulted memory is done without charging. + +Shared hugetlb memory is only uncharged when it is unreserved or deallocated. +This is usually when the hugetlbfs file is deleted, and not when the task that +caused the reservation or fault has exited. -- 2.24.0.rc1.363.gb1bccd3e3d-goog
next prev parent reply other threads:[~2019-10-30 1:37 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-30 1:36 [PATCH v8 1/9] hugetlb_cgroup: Add hugetlb_cgroup reservation counter Mina Almasry 2019-10-30 1:36 ` [PATCH v8 2/9] hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations Mina Almasry 2019-11-08 0:57 ` Mike Kravetz 2019-11-08 23:48 ` Mina Almasry 2019-11-09 0:01 ` Mike Kravetz 2019-11-09 0:40 ` Mina Almasry 2019-11-09 0:46 ` Mike Kravetz 2019-11-25 20:26 ` Mina Almasry 2019-11-26 0:05 ` Mike Kravetz 2019-10-30 1:36 ` [PATCH v8 3/9] hugetlb_cgroup: add cgroup-v2 support Mina Almasry 2019-10-30 1:36 ` [PATCH v8 4/9] hugetlb_cgroup: add reservation accounting for private mappings Mina Almasry 2019-10-30 1:36 ` [PATCH v8 5/9] hugetlb: disable region_add file_region coalescing Mina Almasry 2019-11-01 23:23 ` Mike Kravetz 2019-11-04 21:04 ` Mina Almasry 2019-11-04 21:15 ` Mike Kravetz 2019-11-04 21:19 ` Mina Almasry 2019-11-17 11:03 ` Wenkuan Wang 2019-11-18 19:41 ` Mina Almasry 2019-10-30 1:36 ` [PATCH v8 6/9] hugetlb_cgroup: add accounting for shared mappings Mina Almasry 2019-10-30 1:36 ` [PATCH v8 7/9] hugetlb_cgroup: support noreserve mappings Mina Almasry 2019-10-30 1:37 ` [PATCH v8 8/9] hugetlb_cgroup: Add hugetlb_cgroup reservation tests Mina Almasry 2019-10-30 1:37 ` Mina Almasry [this message] 2019-11-07 23:42 ` [PATCH v8 1/9] hugetlb_cgroup: Add hugetlb_cgroup reservation counter Mike Kravetz 2019-11-08 23:35 ` Mina Almasry
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