linux-kernel - Re: [PATCH v10 00/12] LUF(Lazy Unmap Flush) reducing tlb numbers over 90%

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Date: Sat, 11 May 2024 15:15:01 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Byungchul Park <byungchul@...com>
Cc: <linux-kernel@...r.kernel.org>,  <linux-mm@...ck.org>,
  <kernel_team@...ynix.com>,  <akpm@...ux-foundation.org>,
  <vernhao@...cent.com>,  <mgorman@...hsingularity.net>,
  <hughd@...gle.com>,  <willy@...radead.org>,  <david@...hat.com>,
  <peterz@...radead.org>,  <luto@...nel.org>,  <tglx@...utronix.de>,
  <mingo@...hat.com>,  <bp@...en8.de>,  <dave.hansen@...ux.intel.com>,
  <rjgolo@...il.com>
Subject: Re: [PATCH v10 00/12] LUF(Lazy Unmap Flush) reducing tlb numbers
 over 90%

Byungchul Park <byungchul@...com> writes:

> Hi everyone,
>
> While I'm working with a tiered memory system e.g. CXL memory, I have
> been facing migration overhead esp. tlb shootdown on promotion or
> demotion between different tiers.  Yeah..  most tlb shootdowns on
> migration through hinting fault can be avoided thanks to Huang Ying's
> work, commit 4d4b6d66db ("mm,unmap: avoid flushing tlb in batch if PTE
> is inaccessible").  See the following link for more information:
>
> https://lore.kernel.org/lkml/20231115025755.GA29979@system.software.com/

And, I still have interest of the performance impact of commit
7e12beb8ca2a ("migrate_pages: batch flushing TLB").  In the email above,
you said that the performance of v6.5-rc5 + 7e12beb8ca2a reverted has
better performance than v6.5-rc5.  Can you provide more details?  For
example, the number of TLB flushing IPI for two kernels?

I should have followed up the above email.  Sorry about that.  Anyway,
we should try to fix issue of that commit too.

--
Best Regards,
Huang, Ying

[snip]