From: Andrew Morton <akpm@linux-foundation.org>
To: "Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>
Cc: Shuah Khan <shuah@kernel.org>,
linux-mm@kvack.org, gost.dev@samsung.com,
David Hildenbrand <david@redhat.com>,
willy@infradead.org, mcgrof@kernel.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
Zi Yan <zi.yan@sent.com>, Pankaj Raghav <p.raghav@samsung.com>
Subject: Re: [PATCH v3] selftests/mm: use asm volatile to not optimize mmap read variable
Date: Fri, 7 Jun 2024 21:39:36 -0700 [thread overview]
Message-ID: <20240607213936.a58028617aacdbf6913d3735@linux-foundation.org> (raw)
In-Reply-To: <20240606203619.677276-1-kernel@pankajraghav.com>
On Thu, 6 Jun 2024 20:36:19 +0000 "Pankaj Raghav (Samsung)" <kernel@pankajraghav.com> wrote:
> From: Pankaj Raghav <p.raghav@samsung.com>
>
> create_pagecache_thp_and_fd() in split_huge_page_test.c used the
> variable dummy to perform mmap read.
>
> However, this test was skipped even on XFS which has large folio
> support. The issue was compiler (gcc 13.2.0) was optimizing out the
> dummy variable, therefore, not creating huge page in the page cache.
>
> Use asm volatile() trick to force the compiler not to optimize out
> the loop where we read from the mmaped addr. This is similar to what is
> being done in other tests (cow.c, etc)
>
> As the variable is now used in the asm statement, remove the unused
> attribute.
>
What are the runtime effects of this change? An inappropriate test
failure? If so, shouldn't we fix 6.9.x kernels also? And is
fc4d182316bd ("mm: huge_memory: enable debugfs to split huge pages to
any order") an appropriate Fixes: target?
next prev parent reply other threads:[~2024-06-08 4:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-06 20:36 Pankaj Raghav (Samsung)
2024-06-06 20:52 ` Zi Yan
2024-06-06 21:09 ` David Hildenbrand
2024-06-08 4:39 ` Andrew Morton [this message]
2024-06-08 10:22 ` Pankaj Raghav (Samsung)
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