Differential D11926

Add vm_page_grab_pages()
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Authored by alc on Aug 8 2017, 4:31 PM.

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kib
markj

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rS322296: Introduce vm_page_grab_pages(), which is intended to replace loops calling

Summary

I've made some minor changes from the version that we've discussed in email. I highlight the notable ones below.

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alc created this revision.Aug 8 2017, 4:31 PM

alc added inline comments.Aug 8 2017, 4:37 PM

vm/vm_page.c
3202–3204	I changed the way that this function determines if it needs to sleep on a page. This snippet is copied from vm_page_grab(). In many cases, the old version would perform both vm_page_xbusied() and vm_page_busied(). Now, we always do one or the other, never both.
3213	I made the sleep channel message distinct from vm_page_grab().

kib accepted this revision.Aug 8 2017, 4:40 PM

This revision is now accepted and ready to land.Aug 8 2017, 4:40 PM

markj accepted this revision.Aug 8 2017, 4:41 PM

markj added inline comments.

vm/vm_page.c
3174	The NOBUSY flag description needs to be updated.

Should vm_page_grab_pages() also include this assertion from vm_page_grab():

KASSERT((allocflags & VM_ALLOC_SBUSY) == 0 ||
    (allocflags & VM_ALLOC_IGN_SBUSY) != 0,
    ("vm_page_grab: VM_ALLOC_SBUSY/VM_ALLOC_IGN_SBUSY mismatch"));

Update the description of VM_ALLOC_NOBUSY.

Update the block comment in vm_page.h to reflect the capabilities of vm_page_grab_pages().

This revision now requires review to proceed.Aug 8 2017, 5:02 PM

In D11926#247397, @alc wrote:
Should vm_page_grab_pages() also include this assertion from vm_page_grab():
KASSERT((allocflags & VM_ALLOC_SBUSY) == 0 ||
    (allocflags & VM_ALLOC_IGN_SBUSY) != 0,
    ("vm_page_grab: VM_ALLOC_SBUSY/VM_ALLOC_IGN_SBUSY mismatch"));

I can't see any reason not to, especially if we're considering implementing vm_page_grab() in terms of vm_page_grab_pages(). It might be that there's some valid use-case for specifying ALLOC_SBUSY without ALLOC_IGN_SBUSY, but until that arises it seems reasonable to be strict.

Closed by commit rS322296: Introduce vm_page_grab_pages(), which is intended to replace loops calling (authored by alc). · Explain WhyAug 9 2017, 4:23 AM

This revision was automatically updated to reflect the committed changes.