[...]
Here the @nr_to_scan is reduced by the number of pages that are
isolated, but
not actually reclaimed (which is reflected by @cnt).
IIUC, looks you want to make this function do "each cycle" as what you
mentioned
in the v8 [1]:
I tested with that approach and found we can only target number of
pages
attempted to reclaim not pages actually reclaimed due to the
uncertainty
of how long it takes to reclaim pages. Besides targeting number of
scanned pages for each cycle is also what the ksgxd does.
If we target actual number of pages, sometimes it just takes too long.
I
saw more timeouts with the default time limit when running parallel
selftests.
I am not sure what does "sometimes it just takes too long" mean, but
what I am
thinking is you are trying to do some perfect but yet complicated code
here.
I think what I observed was that the try_charge() would block too long
before getting chance of schedule() to yield, causing more timeouts than
necessary.
I'll do some re-test to be sure.
For instance, I don't think selftest reflect the real workload, and I
believe
adjusting the limit of a given EPC cgroup shouldn't be a frequent
operation,
thus it is acceptable to use some easy-maintain code but less perfect
code.
Here I still think having @nr_to_scan as a pointer is over-complicated.
For
example, we can still let sgx_reclaim_pages() to always scan
SGX_NR_TO_SCAN
pages, but give up when there's enough pages reclaimed or when the EPC
cgroup
and its descendants have been looped:
unsigned int sgx_epc_cgroup_reclaim_pages(struct misc_cg *root)
{
unsigned int cnt = 0;
...
css_for_each_descendant_pre(pos, css_root) {
...
epc_cg = sgx_epc_cgroup_from_misc_cg(css_misc(pos));
cnt += sgx_reclaim_pages(&epc_cg->lru);
if (cnt >= SGX_NR_TO_SCAN)
break;
}
...
return cnt;
}
Yeah it may reclaim more than SGX_NR_TO_SCAN when the loop actually
reaches any
descendants, but that should be rare and we don't care that much, do we?
I assume you meant @cnt here to be number of pages actually reclaimed.
This could cause sgx_epc_cgroup_reclaim_pages() block too long as @cnt
may always be zero (all pages are too young) and you have to loop all
descendants.
Thanks
Haitao
