Remove vmem_size() consumers

There are currently three vmem_size() consumers all of which are
part of the ARC implemention.  However, since the expected behavior
of the Linux and Solaris virtual memory subsystems are so different
the behavior in each of these instances needs to be reevaluated.

* arc_evict_needed() - This is actually dead code.  Arena support
was never added to the SPL and zio_arena is always NULL.  This
support isn't needed so we simply remove this dead code.

* arc_memory_throttle() - On Solaris where virtual memory constitutes
almost all of the address space we can reasonably expect there to be
a fairly large amount free.  However, on Linux by default we only
have about 100MB total and that's heavily used by the ARC.  So the
expectation on Linux is that this will usually be a small value.
Therefore we remove the vmem_size() check for i386 systems because
the expectation is that it will be less than the zfs_write_limit_max.

* arc_init() - Here vmem_size() is used to initially size the ARC.
Since the ARC is currently backed by the virtual address space it
makes sense to use this as a limit on the ARC for 32-bit systems.
This code can be removed when the ARC is backed by the page cache.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #831

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 829b4d9c376470e32f6a831abe0a9294315231a2..6ec9f04b772766998f26bd8a997637f76a2abe4e 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -2414,18 +2414,6 @@ arc_evict_needed(arc_buf_contents_t type)
        if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
                return (1);
 
-#ifdef _KERNEL
-       /*
-        * If zio data pages are being allocated out of a separate heap segment,
-        * then enforce that the size of available vmem for this area remains
-        * above about 1/32nd free.
-        */
-       if (type == ARC_BUFC_DATA && zio_arena != NULL &&
-           vmem_size(zio_arena, VMEM_FREE) <
-           (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
-               return (1);
-#endif
-
        if (arc_no_grow)
                return (1);
 
@@ -3563,10 +3551,6 @@ arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
 
        /* Easily reclaimable memory (free + inactive + arc-evictable) */
        available_memory = ptob(spl_kmem_availrmem()) + arc_evictable_memory();
-#if defined(__i386)
-       available_memory =
-           MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
-#endif
 
        if (available_memory <= zfs_write_limit_max) {
                ARCSTAT_INCR(arcstat_memory_throttle_count, 1);