NeilBrown <neilb@xxxxxxx> wrote:
> Assorted improvements for swap-via-filesystem.
>
> This is a resend of these patches, rebased on current HEAD.
> The only substantial changes is that swap_dirty_folio has replaced
> swap_set_page_dirty.
>
> Currently swap-via-fs (SWP_FS_OPS) doesn't work for any filesystem. It
> has previously worked for NFS but that broke a few releases back.
> This series changes to use a new ->swap_rw rather than ->readpage and
> ->direct_IO. It also makes other improvements.
>
> There is a companion series already in linux-next which fixes various
> issues with NFS. Once both series land, a final patch is needed which
> changes NFS over to use ->swap_rw.
This seems to work by running sufficient copies of the attached program in
parallel to overwhelm the amount of ordinary RAM.
Tested-by: David Howells <dhowells@xxxxxxxxxx>
---
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
int main()
{
unsigned int pid = getpid(), iterations = 0;
size_t i, j, size = 1024 * 1024 * 1024;
char *p;
bool mismatch;
p = malloc(size);
if (!p) {
perror("malloc");
exit(1);
}
srand(pid);
for (i = 0; i < size; i += 4)
*(unsigned int *)(p + i) = rand();
do {
for (j = 0; j < 16; j++) {
for (i = 0; i < size; i += 4096)
*(unsigned int *)(p + i) += 1;
iterations++;
}
mismatch = false;
srand(pid);
for (i = 0; i < size; i += 4) {
unsigned int r = rand();
unsigned int v = *(unsigned int *)(p + i);
if (i % 4096 == 0)
v -= iterations;
if (v != r) {
fprintf(stderr, "mismatch %zx: %x != %x (diff %x)\n",
i, v, r, v - r);
mismatch = true;
}
}
} while (!mismatch);
exit(1);
}
