From: Andrew Morton <akpm@linux-foundation.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: jianhong chen <chenjianhong2@huawei.com>,
linux-mm@kvack.org, Michal Hocko <mhocko@suse.com>,
Vlastimil Babka <vbabka@suse.cz>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
Michel Lespinasse <walken@google.com>
Subject: Re: mm/mmap.c: fix the adjusted length error
Date: Mon, 8 Mar 2021 15:15:09 -0800 [thread overview]
Message-ID: <20210308151509.5b63c7e51a7f41f7fda697dc@linux-foundation.org> (raw)
In-Reply-To: <20210308185002.GD3479805@casper.infradead.org>
On Mon, 8 Mar 2021 18:50:02 +0000 Matthew Wilcox <willy@infradead.org> wrote:
> Hi Andrew,
>
> You have a patch in your tree which I think is a bad idea.
> Link: http://lkml.kernel.org/r/1558073209-79549-1-git-send-email-chenjianhong2@huawei.com
>
> The problem it describes is real -- if you chew up all the address
> space with 64MB pages, free one and then try to allocate another one, it
> will fail. I don't like the solution, though. If memory is fragmented
> in a different way from that described by the patch, it will cause us
> to walk into rbtree nodes that look like they might be able to satisfy
> our allocation, only to find that they cannot, due to alignment issues.
> In the worst case, it turns into a linear scan of the address space
> instead of logarithmic.
>
> I would prefer to see this solved by doing two passes. The first would
> look for a 128MB size hole, as we do now, which is guaranteed to find
> us a 64MB hole if it succeeds. If that search fails, then we can fall
> back to the 64MB hole search, as done in this patch.
OK, thanks. The patch is very old, and stuck. I'll drop it.
prev parent reply other threads:[~2021-03-08 23:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 18:50 Matthew Wilcox
2021-03-08 23:15 ` Andrew Morton [this message]
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