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d95f77f119
The mlx5_fc struct has a cache for values queried from hw, which is
cacheline aligned. On x86_64, this results in:
struct mlx5_fc {
u32 id; /* 0 4 */
bool aging; /* 4 1 */
/* XXX 3 bytes hole, try to pack */
struct mlx5_fc_bulk * bulk; /* 8 8 */
/* XXX 48 bytes hole, try to pack */
/* --- cacheline 1 boundary (64 bytes) --- */
struct mlx5_fc_cache cache __attribute__((__aligned__(64)));
/* 64 24 */
u64 lastpackets; /* 88 8 */
u64 lastbytes; /* 96 8 */
/* size: 128, cachelines: 2, members: 6 */
/* sum members: 53, holes: 2, sum holes: 51 */
/* padding: 24 */
/* forced aligns: 1, forced holes: 1, sum forced holes: 48 */
} __attribute__((__aligned__(64)));
(output from pahole).
...So a 48+24=72 byte waste. As far as I can determine, this serves no
purpose other than maybe making sure that the values in the cache do not
span two cachelines in the worst case scenario, but that's not a valid
enough reason to waste 72 bytes per counter, especially since this code
is not performance-critical. There could potentially be hundreds of
thousands of counters (e.g. for connection-tracking), so this quickly
adds up to multiple MB wasted.
This commit removes the alignment, resulting in:
struct mlx5_fc {
[...]
/* size: 56, cachelines: 1, members: 6 */
/* sum members: 53, holes: 1, sum holes: 3 */
/* last cacheline: 56 bytes */
};
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20241001103709.58127-5-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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 reStructuredText 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.