Date: Thu, 28 Feb 2002 13:14:26 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Jeff Roberson <jroberson@chesapeake.net> Cc: Julian Elischer <julian@elischer.org>, <arch@FreeBSD.ORG> Subject: Re: Slab allocator Message-ID: <200202282114.g1SLEQW38736@apollo.backplane.com> References: <20020228141318.J31751-100000@mail.chesapeake.net>
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:Ok, both of you have requested more comments. I have commented what I
:felt were the trickier situations. Could you give me some examples of
:what seems to be lacking documentation? I'm perfectly willing to add it,
:but since I wrote the code most things seem perfectly intuitive to me. :-)
:
:Thanks,
:Jeff
Could you explain the change made (crinit() and crzero() calls) to
kern/init_main.c ?
Does uma_zalloc() automatically zero the returned memory? You replace
MALLOC(..M_ZERO) in two places, example:
- MALLOC(fp, struct file *, sizeof(struct file), M_FILE, M_WAITOK | M_ZERO
);
+ fp = uma_zalloc(file_zone, M_WAITOK);
I recommend KASSERTing bucket_ub_ptr is in-bounds in vm/uma_core.c
line 1403 (i.e. us_freecount and ub_ptr are coherent).
I recommend KASSERTing that the uz_free_slab list is non-empty
on line 1381.
On line 82 of vm/uma_int.h you describe embedding a slab header
in a Page. I could not find where in the code this embedding
takes place (I looked for 'slab header' in the code but could
not find anything related to the comment on line 82 of vm/uma_int.h
In anycase, if you are embeddeding the slab header I recommend
adding a magic number of the base of the slab header structure
described in the comment and KASSERT()ing it as a sanity check.
-- --
documentation
-- --
uma_timeout line 185 uma_core.c. Could you describe what a
'working set calc.' is? What is a working set?
In general, the comments at the head of the routines do not include
context. For example, take hash_sfind(). 'Find a slab within a zone
that has a matching data field'. What I would like to see is a comment
like this: 'Find a slab within a zone that has a matching data field.
This function is mainly used by the deallocator to locate the slab
which owns an item data pointer.'
Other examples. Line 266, the comment for hash_expand(), says
what it does 'Expands the hash table for OFFPAGE zones', but does
not say WHY it does it or HOW it does it.
In anycase, this is general for all the routines. It would be
nice if you did a once-over and clarified the context of the comment
where it seems appropriate.
-Matt
Matthew Dillon
<dillon@backplane.com>
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