From: Mike Rapoport <rppt@kernel.org>
To: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Rik van Riel <riel@surriel.com>, Michal Hocko <mhocko@kernel.org>,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v2 1/2] mm: cma: allocate cma areas bottom-up
Date: Sun, 20 Dec 2020 08:48:48 +0200 [thread overview]
Message-ID: <20201220064848.GA392325@kernel.org> (raw)
In-Reply-To: <20201217201214.3414100-1-guro@fb.com>
On Thu, Dec 17, 2020 at 12:12:13PM -0800, Roman Gushchin wrote:
> Currently cma areas without a fixed base are allocated close to the
> end of the node. This placement is sub-optimal because of compaction:
> it brings pages into the cma area. In particular, it can bring in hot
> executable pages, even if there is a plenty of free memory on the
> machine. This results in cma allocation failures.
>
> Instead let's place cma areas close to the beginning of a node.
> In this case the compaction will help to free cma areas, resulting
> in better cma allocation success rates.
>
> If there is enough memory let's try to allocate bottom-up starting
> with 4GB to exclude any possible interference with DMA32. On smaller
> machines or in a case of a failure, stick with the old behavior.
>
> 16GB vm, 2GB cma area:
> With this patch:
> [ 0.000000] Command line: root=/dev/vda3 rootflags=subvol=/root systemd.unified_cgroup_hierarchy=1 enforcing=0 console=ttyS0,115200 hugetlb_cma=2G
> [ 0.002928] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node
> [ 0.002930] cma: Reserved 2048 MiB at 0x0000000100000000
> [ 0.002931] hugetlb_cma: reserved 2048 MiB on node 0
>
> Without this patch:
> [ 0.000000] Command line: root=/dev/vda3 rootflags=subvol=/root systemd.unified_cgroup_hierarchy=1 enforcing=0 console=ttyS0,115200 hugetlb_cma=2G
> [ 0.002930] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node
> [ 0.002933] cma: Reserved 2048 MiB at 0x00000003c0000000
> [ 0.002934] hugetlb_cma: reserved 2048 MiB on node 0
>
> v2:
> - switched to memblock_set_bottom_up(true), by Mike
> - start with 4GB, by Mike
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
With one nit below
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
> mm/cma.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index 7f415d7cda9f..21fd40c092f0 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -337,6 +337,22 @@ int __init cma_declare_contiguous_nid(phys_addr_t base,
> limit = highmem_start;
> }
>
> + /*
> + * If there is enough memory, try a bottom-up allocation first.
> + * It will place the new cma area close to the start of the node
> + * and guarantee that the compaction is moving pages out of the
> + * cma area and not into it.
> + * Avoid using first 4GB to not interfere with constrained zones
> + * like DMA/DMA32.
> + */
> + if (!memblock_bottom_up() &&
> + memblock_end >= SZ_4G + size) {
This seems short enough to fit a single line
> + memblock_set_bottom_up(true);
> + addr = memblock_alloc_range_nid(size, alignment, SZ_4G,
> + limit, nid, true);
> + memblock_set_bottom_up(false);
> + }
> +
> if (!addr) {
> addr = memblock_alloc_range_nid(size, alignment, base,
> limit, nid, true);
> --
> 2.26.2
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-12-20 6:49 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 20:12 [PATCH v2 1/2] mm: cma: allocate cma areas bottom-up Roman Gushchin
2020-12-17 20:12 ` [PATCH v2 2/2] memblock: do not start bottom-up allocations with kernel_end Roman Gushchin
2020-12-19 14:52 ` Wonhyuk Yang
2020-12-19 17:05 ` Roman Gushchin
2020-12-20 6:49 ` Mike Rapoport
2021-01-22 4:37 ` Thiago Jung Bauermann
2021-01-24 2:09 ` Andrew Morton
2021-01-24 7:34 ` Mike Rapoport
2021-01-26 0:30 ` Thiago Jung Bauermann
2021-02-08 23:58 ` Thiago Jung Bauermann
2021-02-28 4:18 ` Florian Fainelli
2021-02-28 9:00 ` Mike Rapoport
2021-02-28 18:19 ` Florian Fainelli
2021-02-28 23:08 ` Serge Semin
2021-03-01 3:50 ` Florian Fainelli
2021-03-01 9:22 ` Serge Semin
2021-03-02 4:09 ` Florian Fainelli
2021-03-01 9:45 ` Mike Rapoport
2021-03-02 3:55 ` Roman Gushchin
2020-12-20 6:48 ` Mike Rapoport [this message]
2020-12-21 17:05 ` [PATCH v2 1/2] mm: cma: allocate cma areas bottom-up Roman Gushchin
2020-12-23 4:06 ` Andrew Morton
2020-12-23 16:35 ` Roman Gushchin
2020-12-23 22:10 ` Mike Rapoport
2020-12-28 19:36 ` Roman Gushchin
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