OpenZFS 9284 - arc_reclaim_thread has 2 jobs

Following the fix for 9018 (Replace kmem_cache_reap_now() with
kmem_cache_reap_soon), the arc_reclaim_thread() no longer blocks
while reaping.  However, the code is still confusing and error-prone,
because this thread has two responsibilities.  We should instead
separate this into two threads each with their own responsibility:

 1. keep `arc_size` under `arc_c`, by calling `arc_adjust()`, which
    improves `arc_is_overflowing()`

 2. keep enough free memory in the system, by calling
    `arc_kmem_reap_now()` plus `arc_shrink()`, which improves
    `arc_available_memory()`.

Furthermore, we can use the zthr infrastructure to separate the
"should we do something" from "do it" parts of the logic, and
normalize the start up / shut down of the threads.

Authored by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Tim Kordas <tim.kordas@joyent.com>
Reviewed by: Tim Chase <tim@chase2k.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by:  Brad Lewis <brad.lewis@delphix.com>
Signed-off-by: Brad Lewis <brad.lewis@delphix.com>

OpenZFS-issue: https://www.illumos.org/issues/9284
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/de753e34f9
Closes #8165
This commit is contained in:
Brad Lewis
2017-03-15 16:41:52 -07:00
committed by Brian Behlendorf
parent 00f198de6b
commit 3ec34e5527
7 changed files with 292 additions and 179 deletions
+2
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@@ -163,6 +163,7 @@ extern unsigned int spl_kmem_alloc_max;
#define kmem_alloc(sz, fl) spl_kmem_alloc((sz), (fl), __func__, __LINE__)
#define kmem_zalloc(sz, fl) spl_kmem_zalloc((sz), (fl), __func__, __LINE__)
#define kmem_free(ptr, sz) spl_kmem_free((ptr), (sz))
#define kmem_cache_reap_active spl_kmem_cache_reap_active
extern void *spl_kmem_alloc(size_t sz, int fl, const char *func, int line);
extern void *spl_kmem_zalloc(size_t sz, int fl, const char *func, int line);
@@ -181,5 +182,6 @@ extern void spl_kmem_free_track(const void *buf, size_t size);
extern int spl_kmem_init(void);
extern void spl_kmem_fini(void);
extern int spl_kmem_cache_reap_active(void);
#endif /* _SPL_KMEM_H */
+1
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@@ -773,6 +773,7 @@ typedef int fstrans_cookie_t;
extern fstrans_cookie_t spl_fstrans_mark(void);
extern void spl_fstrans_unmark(fstrans_cookie_t);
extern int __spl_pf_fstrans_check(void);
extern int kmem_cache_reap_active(void);
#define ____cacheline_aligned
+4
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@@ -29,6 +29,7 @@ struct zthr {
kmutex_t zthr_lock;
kcondvar_t zthr_cv;
boolean_t zthr_cancel;
hrtime_t zthr_wait_time;
zthr_checkfunc_t *zthr_checkfunc;
zthr_func_t *zthr_func;
@@ -38,6 +39,9 @@ struct zthr {
extern zthr_t *zthr_create(zthr_checkfunc_t checkfunc,
zthr_func_t *func, void *arg);
extern zthr_t *zthr_create_timer(zthr_checkfunc_t *checkfunc,
zthr_func_t *func, void *arg, hrtime_t nano_wait);
extern void zthr_exit(zthr_t *t, int rc);
extern void zthr_destroy(zthr_t *t);