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charset="utf-8" The real-time(rt) threads are delayed for 5 seconds in mempool_alloc, which will seriously affect the timeliness of front-end applications and the user experience lag issues. The real-time(rt) threads should retry mempool allocation without delay and in order to obtain the required memory resources as soon as possible. The following example shows that the real-time(rt) QoSCoreThread prio=3D98 blocks 5 seconds in mempool_alloc, seriously affecting the user experience. Running process: system_server (pid 2245) Running thread: QoSCoreThread 2529 State: Uninterruptible Sleep - Block I/O Start: 12,859.616 ms Systrace Time: 100,063.057104 Duration: 5,152.591 ms On CPU: Running instead: kswapd0 Args: {kernel callsite when blocked:: "mempool_alloc+0x130/0x1e8"} QoSCoreThread-2529 ( 2245) [000] d..2. 100063.057104: sched_switch: prev_comm=3DQoSCoreThread prev_pid=3D2529 prev_prio=3D000255001000098 prev_state=3DD =3D=3D> next_comm=3Dkswapd0 next_pid=3D107 next_prio=3D000063310000120 [GT]ColdPool#14-23937 ( 23854) [000] dNs2. 100068.209675: sched_waking: comm=3DQoSCoreThread pid=3D2529 prio=3D98 target_cpu=3D000 [GT]ColdPool#14-23937 ( 23854) [000] dNs2. 100068.209676: sched_blocked_reason: pid=3D2529 iowait=3D1 caller=3Dmempool_alloc+0x130/0= x1e8 [GT]ColdPool#14-23937 ( 23854) [000] dNs3. 100068.209695: sched_wakeup: comm=3DQoSCoreThread pid=3D2529 prio=3D98 target_cpu=3D000 [GT]ColdPool#14-23937 ( 23854) [000] d..2. 100068.209732: sched_switch: prev_comm=3D[GT]ColdPool#14 prev_pid=3D23937 prev_prio=3D000003010342130 prev_state=3DR =3D=3D> next_comm=3DQoSCoreThread next_pid=3D2529 next_prio=3D000255131000098 Signed-off-by: Zhiguo Jiang --- mm/mempool.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/mm/mempool.c b/mm/mempool.c --- a/mm/mempool.c +++ b/mm/mempool.c @@ -18,6 +18,7 @@ #include #include #include +#include #include "slab.h" =20 #ifdef CONFIG_SLUB_DEBUG_ON @@ -386,7 +387,7 @@ void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_m= ask) void *element; unsigned long flags; wait_queue_entry_t wait; - gfp_t gfp_temp; + gfp_t gfp_temp, gfp_src =3D gfp_mask; =20 VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO); might_alloc(gfp_mask); @@ -433,6 +434,16 @@ void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_= mask) return NULL; } =20 + /* + * We will try to direct reclaim cyclically, if the rt-thread + * is without __GFP_NORETRY. + */ + if (!(gfp_src & __GFP_NORETRY) && current->prio < MAX_RT_PRIO) { + spin_unlock_irqrestore(&pool->lock, flags); + gfp_temp =3D gfp_src; + goto repeat_alloc; + } + /* Let's wait for someone else to return an element to @pool */ init_wait(&wait); prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); --=20 2.48.1