linux_5_0: restore __kernel_fpu_{begin,restore} #61076

Mic92 · 2019-05-07T05:53:11Z

In 5.0er these function were removed from the public interface also zfs needs
them for AVX/AES-NI support. Without this patch for example throughput on a
encrypted zfs dataset drops to 200 MB/s from 1.2 GB/s. These functions were
removed as there was no user within the linux kernel tree itself.

Motivation for this change

Things done

In 5.0er these function were removed from the public interface also zfs needs them for AVX/AES-NI support. Without this patch for example throughput on a encrypted zfs dataset drops to 200 MB/s from 1.2 GB/s. These functions were removed as their was no user within the linux kernel tree itself.

Mic92 · 2019-05-07T05:55:23Z

pkgs/os-specific/linux/kernel/export_kernel_fpu_functions.patch

+
+ 	kernel_fpu_enable();
+ }
+EXPORT_SYMBOL(__kernel_fpu_end);


The way the zfs build system works is that it just picks up the symbols if they are exported.

tilpner · 2019-06-22T11:11:45Z

Should this be added to older kernels too, now that it was backported to e.g. 4.19.52?

nh2 · 2019-12-02T00:02:29Z

I suspect yes, I see very 100% z_wr_iss CPU usage, see openzfs/zfs#9370.

See also openzfs/zfs#9515.

grahamc · 2019-12-02T00:06:28Z

According to show-derivation, my 19.09 system on 4.19.86 has been patched:

nix show-derivation /nix/store/hv84pqznindpcdc7szgyvh4dinq9ls6w-linux-4.19.86.drv
...
"patches": "/nix/store/mnlqwys9dxznjcvq4w3s0435s9ql8qv8-bridge-stp-helper.patch 
/nix/store/h4c3bag6lv3y47sbx83339xnalmlmdmg-modinst-arg-list-too-long.patch 
/nix/store/l24rm77fgrycjyjwx75b14wk1n4x49p9-export_kernel_fpu_functions.patch 
/nix/store/hdr6v584ig3dpjlcs9afxxky3lvzm2nw-randstruct-provide-seed.patch",

nh2 · 2019-12-02T00:13:29Z

Hmm, indeed my perf top shows me aes_encrypt_intel and aes_aesni_encrypt, suggesting that AES-NI is working as expected.

I'm still surprised the performance is so bad though, I'm maxed out on 100% CPU for z_wr_iss at 100 MB/s.

tilpner · 2019-12-02T07:47:10Z

@nh2 My question from 2019-06-22 was answered elsewhere, and should have been addressed in #63664 and #63665

Introduced in torvalds/linux@aaeca98 with the usual disdain for ZFS. We have been there in the past with <https://www.phoronix.com/news/NixOS-Linux-5.0-ZFS-FPU-Drop> / NixOS#61076. This fixes ZFS on aarch64 until the next breakage. See openzfs/zfs#14555 for original upstream issue.

Mic92 requested a review from fpletz May 7, 2019 05:53

Mic92 commented May 7, 2019

View reviewed changes

ofborg bot added 10.rebuild-darwin: 0 10.rebuild-linux: 11-100 labels May 7, 2019

Mic92 merged commit 2146e10 into NixOS:master May 7, 2019

Mic92 deleted the linux-fpu branch May 7, 2019 09:35

Mic92 mentioned this pull request May 9, 2019

linux_{5_0,5_1,testing}: restore __kernel_fpu_{begin,restore} [19.03] #61187

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RaitoBezarius mentioned this pull request Apr 19, 2023

zfs: offer Linux kernel DRM circumvention option to enable ZFS on 6.2+ #227165

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Mic92 mentioned this pull request Jun 15, 2023

[23.05] zfs: fix evaluation and build on aarch64 systems #237875

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linux_5_0: restore __kernel_fpu_{begin,restore} #61076

linux_5_0: restore __kernel_fpu_{begin,restore} #61076

Mic92 commented May 7, 2019 •

edited

Mic92 May 7, 2019

tilpner commented Jun 22, 2019

nh2 commented Dec 2, 2019

grahamc commented Dec 2, 2019

nh2 commented Dec 2, 2019 •

edited

tilpner commented Dec 2, 2019

linux_5_0: restore __kernel_fpu_{begin,restore} #61076

linux_5_0: restore __kernel_fpu_{begin,restore} #61076

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Mic92 commented May 7, 2019 • edited

Motivation for this change

Things done

Mic92 May 7, 2019

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tilpner commented Jun 22, 2019

nh2 commented Dec 2, 2019

grahamc commented Dec 2, 2019

nh2 commented Dec 2, 2019 • edited

tilpner commented Dec 2, 2019

Mic92 commented May 7, 2019 •

edited

nh2 commented Dec 2, 2019 •

edited