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Restore the UP optimization to reduce the number of TLB invalidations. The

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previous revision only restored the MP optimization.

Describe the optimization strategy for TLB invalidations in a comment.

Reviewed by: ups@
MFC after: 3 days
This commit is contained in:
Alan Cox 2005-10-13 23:42:12 +00:00
parent 20a65f37a0
commit c71c8706fe
1 changed files with 11 additions and 4 deletions
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15
sys/i386/i386/vm_machdep.c
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@ -705,14 +705,21 @@ sf_buf_alloc(struct vm_page *m, int flags)
/*
* Update the sf_buf's virtual-to-physical mapping, flushing the
* virtual address from the TLB. Since the reference count for
* virtual address from the TLB. Since the reference count for
* the sf_buf's old mapping was zero, that mapping is not
* currently in use. Consequently, there is no need to exchange
* currently in use. Consequently, there is no need to exchange
* the old and new PTEs atomically, even under PAE.
*/
ptep = vtopte(sf->kva);
opte = *ptep;
*ptep = VM_PAGE_TO_PHYS(m) | pgeflag | PG_RW | PG_V;
/*
* Avoid unnecessary TLB invalidations: If the sf_buf's old
* virtual-to-physical mapping was not used, then any processor
* that has invalidated the sf_buf's virtual address from its TLB
* since the last used mapping need not invalidate again.
*/
#ifdef SMP
if ((opte & (PG_V | PG_A)) == (PG_V | PG_A))
sf->cpumask = 0;
@ -723,7 +730,6 @@ shootdown:
sf->cpumask |= cpumask;
invlpg(sf->kva);
}
if ((flags & SFB_CPUPRIVATE) == 0) {
other_cpus = PCPU_GET(other_cpus) & ~sf->cpumask;
if (other_cpus != 0) {
@ -735,7 +741,8 @@ shootdown:
}
sched_unpin();
#else
pmap_invalidate_page(kernel_pmap, sf->kva);
if ((opte & (PG_V | PG_A)) == (PG_V | PG_A))
pmap_invalidate_page(kernel_pmap, sf->kva);
#endif
done:
mtx_unlock(&sf_buf_lock);