Faster page faulting through prezeroing [LWN.net]

Faster page faulting through prezeroing

Posted Jan 13, 2005 11:26 UTC (Thu) by etienne (subscriber, #25256)
In reply to: Faster page faulting through prezeroing by huaz
Parent article: Faster page faulting through prezeroing

<quote>The what happens when kscrubd wakes up and clears the pages? Yup, it brings the memory into cache and might get evicted before someone needs it</quote>

Maybe that is not the job of the processor to clear the page, for instance kscrubd function can do a IDE DMA read on the disk of a pre-zeroed area. Then the processor cache is not touched (could be marked dirty but...). That pre-zeroed area could be some reserved blocks at the end of the swap partition, or a contigous file.

Another clean solution is available on non ia32 processor, being write and invalidate instruction: when the first byte of a cache line is written (to zero), the complete cache line is not first read from memory.
IMHO, when the repeat counter (in register %ecx) is bigger than the cache line, assembly instruction "rep stosl" still do not produce a write and invalidate transaction to external memory on ia32.

Etienne.

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