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a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=yJojWOMRYYMA:10 a=GoEa3M9JfhUA:10 a=pGLkceISAAAA:8 a=7CQSdrXTAAAA:8 a=mzZxRmUfWSig62SmEuQA:9 a=a-qgeE7W1pNrGK8U0ZQC:22 cc=ntf awl=host:12083 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTA4MDE2NSBTYWx0ZWRfXyGBZr90obn+j Mlp/sqz9GcQNDFgRX/Nt0JtmEsyWXU4hyhZWQEc4Y+qtrisanyEG83wBjbYSKvcg5N8Rc5zMd0F xclZ0zm9FMLTAy/gjjT7mV5pYOr1mOQlynshP5GeC0yDOOVWlfRmyC/4Ogul1/aSjOqY8hPY/8u nf4rnBWUXAarCTyeBj5hmSkZ2iYN4xYwNT5kEyMwruHDk9s7Cy02egXFkUjVk1pUgI7WZZZSanL IncfgXAp2+TFDlklerEQzD1n65y8ZvFEOWxGwoqQSeD+gppvAYiuse3R8o/70SHGfr2ACpg+j93 sl841eIDwgW6GeY9ucOWOqjHUdvqfjfbCegKjJ/DtoffWrm424Ii4ie9qZwOet++c63eoLnYXJI aiqBt22tB00r1swKO6lweqMWLBN4oQ== X-Proofpoint-GUID: Lh0NusTMpgasmOzw_Jg8HeIHO5iwI1sh X-Proofpoint-ORIG-GUID: Lh0NusTMpgasmOzw_Jg8HeIHO5iwI1sh Kumar Kartikeya Dwivedi writes: > On Thu, 11 Sept 2025 at 16:32, Catalin Marinas wrote: >> >> On Wed, Sep 10, 2025 at 08:46:55PM -0700, Ankur Arora wrote: >> > Switch out the conditional load inerfaces used by rqspinlock >> > to smp_cond_read_acquire_timeout(). >> > This interface handles the timeout check explicitly and does any >> > necessary amortization, so use check_timeout() directly. >> >> It's worth mentioning that the default smp_cond_load_acquire_timeout() >> implementation (without hardware support) only spins 200 times instead >> of 16K times in the rqspinlock code. That's probably fine but it would >> be good to have confirmation from Kumar or Alexei. >> > > This looks good, but I would still redefine the spin count from 200 to > 16k for rqspinlock.c, especially because we need to keep > RES_CHECK_TIMEOUT around which still uses 16k spins to amortize > check_timeout. By my count that amounts to ~100us per check_timeout() on x86 systems I've tested with cpu_relax(). Which seems quite reasonable. 16k also seems safer on CPUs where cpu_relax() is basically a NOP. -- ankur