Messages in this thread | | | Date | Wed, 3 Jan 2007 08:20:09 -0500 (EST) | From | "Robert P. J. Day" <> | Subject | Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear_page()"? |
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On Sun, 31 Dec 2006, Arjan van de Ven wrote:
> So... yes I fully agree with you that it's worth looking at the > memset( , PAGE_SIZE) users. If they are page aligned, yes absolutely > make it a clear_page(), I think that's a very good idea. However > also please check if they've been very recently allocated in that > code, and if maybe the zeroing allocators are better suited there.. > (or maybe there's even double zeroing going on.. that's be a nice > gain)
there's certainly some cleanup/speedup that could be done regarding these numerous "memset(...,0,PAGE_SIZE) calls.
first, there the obvious 1:1 replacement with a call to "clear_page()" ***if that's appropriate***.
second, there's some possible simplification, given snippets like this one from arch/sparc/mm/sun4c.c
pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT); if (pte) memset(pte, 0, PAGE_SIZE);
which seems to be an obvious candidate for replacement with:
pte = get_zeroed_page(GFP_KERNEL|__GFP_REPEAT)
no?
finally, there is certainly some "double zeroing" going on, as with this snippet from drivers/atm/eni.c:
... eni_dev->rx_map = (struct atm_vcc **) get_zeroed_page(GFP_KERNEL); ^^^^^^^^^^^^^^^ if (!eni_dev->rx_map) { printk(KERN_ERR DEV_LABEL "(itf %d): couldn't get free page\n", dev->number); free_page((unsigned long) eni_dev->free_list); return -ENOMEM; } memset(eni_dev->rx_map,0,PAGE_SIZE); // redundant, no? ...
so, yes, there does appear to be room for cleanup/speedup.
rday
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