On 07.08.24 23:58, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx>
Zhiguo reported that swap release could be a serious bottleneck
during process exits[1]. With mTHP, we have the opportunity to
batch free swaps.
Thanks to the work of Chris and Kairui[2], I was able to achieve
this optimization with minimal code changes by building on their
efforts.
If swap_count is 1, which is likely true as most anon memory are
private, we can free all contiguous swap slots all together.
Ran the below test program for measuring the bandwidth of munmap
using zRAM and 64KiB mTHP:
#include <sys/mman.h>
#include <sys/time.h>
#include <stdlib.h>
unsigned long long tv_to_ms(struct timeval tv)
{
return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}
main()
{
struct timeval tv_b, tv_e;
int i;
#define SIZE 1024*1024*1024
void *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (!p) {
perror("fail to get memory");
exit(-1);
}
madvise(p, SIZE, MADV_HUGEPAGE);
memset(p, 0x11, SIZE); /* write to get mem */
madvise(p, SIZE, MADV_PAGEOUT);
gettimeofday(&tv_b, NULL);
munmap(p, SIZE);
gettimeofday(&tv_e, NULL);
printf("munmap in bandwidth: %ld bytes/ms\n",
SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b)));
}
The result is as below (munmap bandwidth):
mm-unstable mm-unstable-with-patch
round1 21053761 63161283
round2 21053761 63161283
round3 21053761 63161283
round4 20648881 67108864
round5 20648881 67108864
munmap bandwidth becomes 3X faster.
[1] https://lore.kernel.org/linux-mm/20240731133318.527-1-justinjiang@xxxxxxxx/
[2] https://lore.kernel.org/linux-mm/20240730-swap-allocator-v5-0-cb9c148b9297@xxxxxxxxxx/
Cc: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
All looks straight forward to me
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Cheers,
David / dhildenb
