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SubjectRe: Clearing the I/O caches? (for benchmark tests)
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"Stephen C. Tweedie" <sct@redhat.com> writes:
> On 14 Jul 1999 16:42:47 -0700, tmk@cse.ucsc.edu (Tom M. Kroeger) said:
>
> > In any case the memory exhausting approach still cleared far more
> > space than sys_sync & invalidate_buffers etc... (are these buffers
> > taken from ext2 when memory becomes very low?) Any idea as to why?
>
> Of course it will. Invalidating buffers etc. won't do anything about
> the page cache. A memory flush will also flush out the page cache very
> effectvely.

My apologies, I may have been unclear. I've been trying to clear all
the cache data and have been calling the following: to reduce the

dcache -- prune_dcache(0);

page cache -- empty_dcache(); -- a clone of prune dcache that calls
clear_inode_pages() for each dcache entry
-- and/or a modified shrink_mmap() that
if (xxxx_under_min()) removed and (below)
inode cache -- free_inode_memory(20);

buffer cache -- sys_sync(); & invalidate_all_buffers();

all in an order something like this.

Is there a better way you'd recommend for clearing the cached I/O
data? I suspect the best things seems to be a reboot, and then memory
exhaust will suffice as an approximation despite its side effects.

In any case, sincerely thanks for your patience and help,

--

tmk

-----------------------------------------------------------------------
Tom M. Kroeger Pray for wind
Graduate Student, UC Santa Cruz \ Pray for waves
e-mail: tmk@cs.ucsc.edu |\ and Pray it's your day off!
http://www.cse.ucsc.edu/~tmk |~\
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(831) 426-9055 home ,----+--


int shrink_mmap_all( void)
{
struct page * page;
int i;
i = max_mapnr;
while (i-- > 0) {
int referenced;
page = mem_map +i;

/* This works even in the presence of PageSkip because
* the first two entries at the beginning of a hole will
* be marked, not just the first.
*/
if (PageSkip(page)) {
continue;
}
referenced = test_and_clear_bit(PG_referenced, &page->flags);

if (PageLocked(page))
continue;
/* We can't free pages unless there's just one user */
if (atomic_read(&page->count) != 1)
continue;
if (PageSwapCache(page)) {
if (referenced && swap_count(page->offset) != 1)
continue;
delete_from_swap_cache(page);
continue;
}
if (referenced)
continue;
/* Is it a buffer page? */
if (page->buffers) {
debug(11,"buffer page %d\n",i);
free_buffers(page);
continue;
}
/* is it a page-cache page? */
if (page->inode) {
remove_inode_page(page);
}
}
return 0;
}
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