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Yonghong Song c39aa3b289 bpf: Allow per unit prefill for non-fix-size percpu memory allocator 
Commit 41a5db8d81 ("Add support for non-fix-size percpu mem allocation")
added support for non-fix-size percpu memory allocation.
Such allocation will allocate percpu memory for all buckets on all
cpus and the memory consumption is in the order to quadratic.
For example, let us say, 4 cpus, unit size 16 bytes, so each
cpu has 16 * 4 = 64 bytes, with 4 cpus, total will be 64 * 4 = 256 bytes.
Then let us say, 8 cpus with the same unit size, each cpu
has 16 * 8 = 128 bytes, with 8 cpus, total will be 128 * 8 = 1024 bytes.
So if the number of cpus doubles, the number of memory consumption
will be 4 times. So for a system with large number of cpus, the
memory consumption goes up quickly with quadratic order.
For example, for 4KB percpu allocation, 128 cpus. The total memory
consumption will 4KB * 128 * 128 = 64MB. Things will become
worse if the number of cpus is bigger (e.g., 512, 1024, etc.)

In Commit 41a5db8d81, the non-fix-size percpu memory allocation is
done in boot time, so for system with large number of cpus, the initial
percpu memory consumption is very visible. For example, for 128 cpu
system, the total percpu memory allocation will be at least
(16 + 32 + 64 + 96 + 128 + 196 + 256 + 512 + 1024 + 2048 + 4096)
  * 128 * 128 = ~138MB.
which is pretty big. It will be even bigger for larger number of cpus.

Note that the current prefill also allocates 4 entries if the unit size
is less than 256. So on top of 138MB memory consumption, this will
add more consumption with
3 * (16 + 32 + 64 + 96 + 128 + 196 + 256) * 128 * 128 = ~38MB.
Next patch will try to reduce this memory consumption.

Later on, Commit 1fda5bb66a ("bpf: Do not allocate percpu memory
at init stage") moved the non-fix-size percpu memory allocation
to bpf verificaiton stage. Once a particular bpf_percpu_obj_new()
is called by bpf program, the memory allocator will try to fill in
the cache with all sizes, causing the same amount of percpu memory
consumption as in the boot stage.

To reduce the initial percpu memory consumption for non-fix-size
percpu memory allocation, instead of filling the cache with all
supported allocation sizes, this patch intends to fill the cache
only for the requested size. As typically users will not use large
percpu data structure, this can save memory significantly.
For example, the allocation size is 64 bytes with 128 cpus.
Then total percpu memory amount will be 64 * 128 * 128 = 1MB,
much less than previous 138MB.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231222031745.1289082-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2024-01-03 21:08:25 -08:00
arch net/sched: Remove CONFIG_NET_ACT_IPT from default configs 2024-01-02 12:41:16 +00:00
block block-6.7-2023-12-01 2023-12-02 06:39:30 +09:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression in ahash and hides the Kconfig sub-options for the jitter RNG. 2023-11-09 17:04:58 -08:00
Documentation dt-bindings: net: renesas,etheravb: Document RZ/G3S support 2024-01-02 14:19:56 -08:00
drivers ppp: Fix spelling typo in comment in ppp_async_encode() 2024-01-02 16:26:09 -08:00
fs Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2023-12-21 22:17:23 +01:00
include bpf: Allow per unit prefill for non-fix-size percpu memory allocator 2024-01-03 21:08:25 -08:00
init As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
io_uring io_uring/cmd: fix breakage in SOCKET_URING_OP_SIOC* implementation 2023-12-14 16:52:13 -07:00
ipc Many singleton patches against the MM code. The patch series which are 2023-11-02 19:38:47 -10:00
kernel bpf: Allow per unit prefill for non-fix-size percpu memory allocator 2024-01-03 21:08:25 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2023-12-21 22:17:23 +01:00
LICENSES
mm Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2023-12-21 22:17:23 +01:00
net bpf: sockmap, fix proto update hook to avoid dup calls 2024-01-03 16:50:06 -08:00
rust net: phy: add Rust Asix PHY driver 2023-12-15 09:35:50 +00:00
samples samples/bpf: Use %lu format specifier for unsigned long values 2023-12-20 15:28:59 +01:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2023-12-14 17:14:41 -08:00
security Revert BPF token-related functionality 2023-12-19 08:23:03 -08:00
sound ALSA: hda/tas2781: reset the amp before component_add 2023-12-14 12:04:38 +01:00
tools bpf: sockmap, add tests for proto updates replace socket 2024-01-03 16:50:22 -08:00
usr arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
virt Revert "KVM: Prevent module exit until all VMs are freed" 2023-12-01 08:12:30 -08:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: generate kernel.spec in rpmbuild/SPECS/ 2023-10-03 20:49:09 +09:00
.mailmap mailmap: add entries for Geliang Tang 2023-12-17 20:54:22 +00:00
.rustfmt.toml
COPYING
CREDITS MAINTAINERS: drop Antti Palosaari 2023-12-06 16:12:49 -08:00
Kbuild
Kconfig
MAINTAINERS octeon_ep_vf: update MAINTAINERS 2024-01-02 14:19:54 +00:00
Makefile Linux 6.7-rc6 2023-12-17 15:19:28 -08:00
README

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.