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Optimize HPTS so that little work is done until we have a hpts thread that is over the connection threshold

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HPTS inserts a softclock for system call return that optimizes performance. However when
no HPTS threads need the help (i.e. when they have less than 100 or so connections) then
there should be little work done i.e. check the counter and return instead of running through
all the threads getting locks etc.ptimize HPTS so that little work is done until we have a hpts
thread that is over the connection threshold.

Reported by:    eduardo
Reviewed by:    gallatin, glebius, tuexen
Tested by:      gallatin
Differential Revision: https://reviews.freebsd.org/D44420
This commit is contained in:
Randall Stewart 2024-03-28 08:12:37 -04:00
parent 1c091d1126
commit b7b78c1c16
3 changed files with 14 additions and 2 deletions
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2
sys/kern/subr_trap.c
View file

@ -74,6 +74,8 @@
#include <sys/epoch.h>
#endif
volatile uint32_t __read_frequently hpts_that_need_softclock = 0;
void (*tcp_hpts_softclock)(void);
/*

10
sys/netinet/tcp_hpts.c
View file

@ -193,7 +193,8 @@ struct tcp_hpts_entry {
uint8_t p_direct_wake :1, /* boolean */
p_on_min_sleep:1, /* boolean */
p_hpts_wake_scheduled:1, /* boolean */
p_avail:5;
hit_callout_thresh:1,
p_avail:4;
uint8_t p_fill[3]; /* Fill to 32 bits */
/* Cache line 0x40 */
struct hptsh {
@ -1683,6 +1684,13 @@ tcp_hpts_thread(void *ctx)
ticks_ran = tcp_hptsi(hpts, 1);
tv.tv_sec = 0;
tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
if ((hpts->p_on_queue_cnt > conn_cnt_thresh) && (hpts->hit_callout_thresh == 0)) {
hpts->hit_callout_thresh = 1;
atomic_add_int(&hpts_that_need_softclock, 1);
} else if ((hpts->p_on_queue_cnt <= conn_cnt_thresh) && (hpts->hit_callout_thresh == 1)) {
hpts->hit_callout_thresh = 0;
atomic_subtract_int(&hpts_that_need_softclock, 1);
}
if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
if(hpts->p_direct_wake == 0) {
/*

4
sys/sys/systm.h
View file

@ -400,8 +400,10 @@ extern int cpu_disable_c2_sleep;
extern int cpu_disable_c3_sleep;
extern void (*tcp_hpts_softclock)(void);
extern volatile uint32_t __read_frequently hpts_that_need_softclock;
#define tcp_hpts_softclock() do { \
if (tcp_hpts_softclock != NULL) \
if (hpts_that_need_softclock > 0) \
tcp_hpts_softclock(); \
} while (0)