On 2024/6/10 20:10, Daniel Gomez wrote:
Hi Baolin,
On Tue, Jun 04, 2024 at 06:17:44PM +0800, Baolin Wang wrote:
Anonymous pages have already been supported for multi-size (mTHP) allocation
through commit 19eaf44954df, that can allow THP to be configured through the
sysfs interface located at '/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled'.
However, the anonymous shmem will ignore the anonymous mTHP rule configured
through the sysfs interface, and can only use the PMD-mapped THP, that is not
reasonable. Many implement anonymous page sharing through mmap(MAP_SHARED |
MAP_ANONYMOUS), especially in database usage scenarios, therefore, users expect
to apply an unified mTHP strategy for anonymous pages, also including the
anonymous shared pages, in order to enjoy the benefits of mTHP. For example,
lower latency than PMD-mapped THP, smaller memory bloat than PMD-mapped THP,
contiguous PTEs on ARM architecture to reduce TLB miss etc.
As discussed in the bi-weekly MM meeting[1], the mTHP controls should control
all of shmem, not only anonymous shmem, but support will be added iteratively.
Therefore, this patch set starts with support for anonymous shmem.
The primary strategy is similar to supporting anonymous mTHP. Introduce
a new interface '/mm/transparent_hugepage/hugepage-XXkb/shmem_enabled',
which can have almost the same values as the top-level
'/sys/kernel/mm/transparent_hugepage/shmem_enabled', with adding a new
additional "inherit" option and dropping the testing options 'force' and
'deny'. By default all sizes will be set to "never" except PMD size, which
is set to "inherit". This ensures backward compatibility with the anonymous
shmem enabled of the top level, meanwhile also allows independent control of
anonymous shmem enabled for each mTHP.
Use the page fault latency tool to measure the performance of 1G anonymous shmem
I'm not familiar with this tool. Could you share which repo/tool you are
referring to?
Sure. The git repo is: https://github.com/gormanm/pft.git
And I did a little changes to test anon shmem:
diff --git a/pft.c b/pft.c
index 3ab1457..bbcd7e6 100644
--- a/pft.c
+++ b/pft.c
@@ -739,7 +739,7 @@ alloc_test_memory(void)
int j;
if (do_shm) {
- if (p = alloc_shm(bytes)) {
+ if (p = valloc_shared(bytes)) {
do_mbind(p, bytes);
do_noclear(p, bytes);
}
Also, are you running or are you aware of any other tools/tests available for
shmem that we can use to make sure we do not introduce any regressions?
I did run the mm selftest cases, as well as some testing cases I wrote
for anon shmem.
