+{
size_t size = (size_t)arg;char *mem = (char *)malloc(size);int ret = 0;if (!mem)return -1;for (int i = 0; i < size; i += 4095)mem[i] = 'a';cgroup_util.h defines PAGE_SIZE, see alloc_anon() for example.
On that note, alloc_anon() is awfully close to allocate_bytes() below, perhaps we should consolidate them. The only difference I see is that alloc_anon() does not check for the allocation failure, but a lot of functions in cgroup_helpers.c don't, so it seems intentional for simplification.
Hmm I didn't know about this function. I think it was Domenico who added allocate_bytes() for the initial zswap tests, and I've just been piggybacking on it ever since: https://github.com/torvalds/linux/commit/d9cfaf405b8ffe2c716b1ce4c82e0a19d50...
I can send a separate patch to clean this up later :) Doesn't seem that bad.
SGTM.
[..]
if (cg_write(test_group, "memory.zswap.max", "0"))goto out;/* Allocate and read more than memory.max to trigger swapin */if (cg_run(test_group, allocate_bytes_and_read, (void *)MB(32)))goto out;/* Verify that no zswap happened */If we want to be really meticulous, we can verify that we did swap out, but not to zswap. IOW, we can check memory.swap.current or something.
Hmm would memory.swap.current go back to 0 once the memory-in-swap is freed? It doesn't seem like we have any counters at the cgroup level for swapout/swapin events. Maybe such counters were not useful enough to justify the extra overhead of maintaining them? :)
Anyway, I think checking zswpout should probably be enough here. That's the spirit of the test anyway - make absolutely sure that no zswap-out happened.
The test is making sure that even though we used real swap, we did not use zswap. In other words, we may see a false positive if something goes wrong and we don't swap anything at all. I know I am probably being paranoid here :)
How about we check memory.swap.peak?
[..]
test_group = cg_name(root, "zswapin_test");if (!test_group)goto out;if (cg_create(test_group))goto out;if (cg_write(test_group, "memory.max", "8M"))goto out;if (cg_write(test_group, "memory.zswap.max", "max"))goto out;/* Allocate and read more than memory.max to trigger (z)swap in */if (cg_run(test_group, allocate_bytes_and_read, (void *)MB(32)))goto out;We should probably check for a positive zswapin here, no?
Oh right. I'll just do a quick check here:
zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin "); if (zswpin < 0) { ksft_print_msg("Failed to get zswpin\n"); goto out; }
if (zswpin == 0) { ksft_print_msg("zswpin should not be 0\n"); goto out; }
SGTM.
Thanks!