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Eric Dumazet says: ==================== net: reduce tcp_memory_allocated inflation Hosts with a lot of sockets tend to hit so called TCP memory pressure, leading to very bad TCP performance and/or OOM. The problem is that some TCP sockets can hold up to 2MB of 'forward allocations' in their per-socket cache (sk->sk_forward_alloc), and there is no mechanism to make them relinquish their share under mem pressure. Only under some potentially rare events their share is reclaimed, one socket at a time. In this series, I implemented a per-cpu cache instead of a per-socket one. Each CPU has a +1/-1 MB (256 pages on x86) forward alloc cache, in order to not dirty tcp_memory_allocated shared cache line too often. We keep sk->sk_forward_alloc values as small as possible, to meet memcg page granularity constraint. Note that memcg already has a per-cpu cache, although MEMCG_CHARGE_BATCH is defined to 32 pages, which seems a bit small. Note that while this cover letter mentions TCP, this work is generic and supports TCP, UDP, DECNET, SCTP. ==================== Link: https://lore.kernel.org/r/20220609063412.2205738-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
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| include | ||
| init | ||
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| kernel | ||
| lib | ||
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| net | ||
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| virt | ||
| .clang-format | ||
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| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.