News: 0001490828

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GNU C Library Tuning For AArch64 Helps Memset Performance By ~24%

([GNU] 5 Hours Ago Glibc AArch64 memset Optimization)


A patch merged yesterday to the GNU C Library (glibc) codebase can help the memset() function's performance by 24% as measured on an Arm Neoverse-N1 core.

Wilco Dijkstra of Arm has landed a memset optimization for the AArch64 code within the GNU C Library. Wilco explains in [1]the patch adjusting the hand-tuned Assembly code:

"Improve small memsets by avoiding branches and use overlapping stores. Use DC ZVA for copies over 128 bytes. Remove unnecessary code for ZVA sizes other than 64 and 128. Performance of random memset benchmark improves by 24% on Neoverse N1."

It will be interesting to see the memset performance impact of this optimization on other Arm cores as well.

The Neoverse-N1 is what's found in the Ampere Altra / Ampere Altra Max servers among other SoCs and thus will be nice to see this optimization rolling out in the next Glibc release. That next release will be Glibc 2.41 and should be out around February.



[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=cec3aef32412779e207f825db0d057ebb4628ae8



Phoronos

Veto

By the middle 1880's, practically all the roads except those in
the South, were of the present standard gauge. The southern roads were
still five feet between rails.
It was decided to change the gauge of all southern roads to standard,
in one day. This remarkable piece of work was carried out on a Sunday in May
of 1886. For weeks beforehand, shops had been busy pressing wheels in on the
axles to the new and narrower gauge, to have a supply of rolling stock which
could run on the new track as soon as it was ready. Finally, on the day set,
great numbers of gangs of track layers went to work at dawn. Everywhere one
rail was loosened, moved in three and one-half inches, and spiked down in its
new position. By dark, trains from anywhere in the United States could operate
over the tracks in the South, and a free interchange of freight cars everywhere
was possible.
-- Robert Henry, "Trains", 1957