On 15.04.24 10:59, Kefeng Wang wrote:
On 2024/4/15 16:18, Barry Song wrote:
On Mon, Apr 15, 2024 at 8:12 PM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
Both the file pages and anonymous pages support large folio, high-order
pages except PMD_ORDER will also be allocated frequently which could
increase the zone lock contention, allow high-order pages on pcp lists
could reduce the big zone lock contention, but as commit 44042b449872
("mm/page_alloc: allow high-order pages to be stored on the per-cpu lists")
pointed, it may not win in all the scenes, add a new control sysfs to
enable or disable specified high-order pages stored on PCP lists, the order
(PAGE_ALLOC_COSTLY_ORDER, PMD_ORDER) won't be stored on PCP list by default.
This is precisely something Baolin and I have discussed and intended
to implement[1],
but unfortunately, we haven't had the time to do so.
Indeed, same thing. Recently, we are working on unixbench/lmbench
optimization, I tested Multi-size THP for anonymous memory by hard-cord
PAGE_ALLOC_COSTLY_ORDER from 3 to 4[1], it shows some improvement but
not for all cases and not very stable, so re-implemented it by according
to the user requirement and enable it dynamically.
I'm wondering, though, if this is really a suitable candidate for a
sysctl toggle. Can anybody really come up with an educated guess for
these values?
Especially reading "Benchmarks Score shows a little improvoment(0.28%)"
and "it may not win in all the scenes", to me it mostly sounds like
"minimal impact" -- so who cares?
How much is the cost vs. benefit of just having one sane system
configuration?
--
Cheers,
David / dhildenb
