On 01/25/2016 11:49 AM, David Howells wrote:
> From: NeilBrown <neilb@xxxxxxx>
>
> When cachefilesd finds that it needs to cull, but that culling doesn't
> achieve anything, it sets an alarm to wake it in 30 seconds to try again.
> But as read_cache_state() will detect that culling is still needed, it will
> immediately try again anyway.
>
> This results in 100% cpu usage of no value.
>
> This patch causes culling to be blocked until the 30 second alarm goes off.
>
> It also changes the test to decide whether to enter poll() after blocking
> signals to test exactly those values that might be changed by a signal.
> Testing these is important, testing anything else is pointless.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: John Snow <jsnow@xxxxxxxxxx>
> ---
>
> cachefilesd.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/cachefilesd.c b/cachefilesd.c
> index 6658ba5..eaa1bb0 100644
> --- a/cachefilesd.c
> +++ b/cachefilesd.c
> @@ -99,6 +99,7 @@ static struct object **cullready;
> static unsigned nr_in_build_table;
> static unsigned nr_in_ready_table;
> static int ncullable;
> +static bool cull_delayed;
>
>
> static const char *configfile = "/etc/cachefilesd.conf";
> @@ -246,6 +247,7 @@ static void sigio(int sig)
> static void sigalrm(int sig)
> {
> jumpstart_scan = true;
> + cull_delayed = false;
> }
>
> /*****************************************************************************/
> @@ -613,11 +615,11 @@ static void cachefilesd(void)
>
> /* sleep without racing on reap and cull with the signal
> * handlers */
> - if (!scan && !reap && !cull) {
> + if (!scan && !reap && !(cull && !cull_delayed)) {
> if (sigprocmask(SIG_BLOCK, &sigs, &osigs) < 0)
> oserror("Unable to block signals");
>
> - if (!reap && !cull) {
> + if (!reap && !stop && !jumpstart_scan) {
> if (ppoll(pollfds, 1, NULL, &osigs) < 0 &&
> errno != EINTR)
> oserror("Unable to suspend process");
> @@ -644,7 +646,7 @@ static void cachefilesd(void)
> if (cull) {
> if (nr_in_ready_table > 0)
> cull_objects();
> - else if (nr_in_build_table == 0)
> + else if (nr_in_build_table == 0 && !cull_delayed)
> jumpstart_scan = true;
> }
>
> @@ -1364,6 +1366,7 @@ static void decant_cull_table(void)
>
> /* if nothing there, scan again in a short while */
> if (nr_in_build_table == 0) {
> + cull_delayed = true;
> signal(SIGALRM, sigalrm);
> alarm(30);
> return;
>
> --
> Linux-cachefs mailing list
> Linux-cachefs@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/linux-cachefs
>
--
—js
--
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