From: Uladzislau Rezki <urezki@gmail.com>
To: Michel Lespinasse <walken@google.com>
Cc: Uladzislau Rezki <urezki@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Peter Zijlstra <peterz@infradead.org>,
David Howells <dhowells@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/3] augmented rbtree: add new RB_DECLARE_CALLBACKS_MAX macro
Date: Wed, 31 Jul 2019 16:20:11 +0200 [thread overview]
Message-ID: <20190731140948.xtuwtfsjth5ecgo3@pc636> (raw)
In-Reply-To: <CANN689FMTh=Odn-KM06bPAf9zFwOpSg3FthL7Q5OXRGVWQUOhg@mail.gmail.com>
Hello, Michel.
>
> Hmmm, I had not thought about that. Agree that this can be useful -
> there is already similar test code in rbtree_test.c and also
> vma_compute_subtree_gap() in mmap.c, ...
>
> With patch 3/3 of this series, the RBCOMPUTE function (typically
> generated through the RB_DECLARE_CALLBACKS_MAX macro) will return a
> bool indicating if the node's augmented value was already correctly
> set. Maybe this can be used for test code, through in the false case,
> the node's augmented value is already overwritten with the correct
> value. Not sure if that is a problem though - the files I mentioned
> above have test code that will dump the values if there is a mismatch,
> but really I think in every realistic case just noting that there was
> one would be just as helpful as being able to dump the old (incorrect)
> value....
>
> What do you think - is the RBCOMPUTE(node, true) function sufficient
> for such debugging ?
>
I think so, at least i do not see any issues with that. If it returns
"false" then it will indicate that the node was not correctly augmented.
Also, i see in many places across your patches there is below code:
<snip>
RBSTRUCT *child; \
RBTYPE max = RBCOMPUTE(node); \
if (node->RBFIELD.rb_left) { \
child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD); \
if (child->RBAUGMENTED > max) \
max = child->RBAUGMENTED; \
} \
if (node->RBFIELD.rb_right) { \
child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD); \
if (child->RBAUGMENTED > max) \
max = child->RBAUGMENTED; \
} \
if (exit && node->RBAUGMENTED == max) \
return true; \
node->RBAUGMENTED = max; \
return false;
<snip>
i think it can be simplified by using max3 macro. For example:
<snip>
get_subtree_max(struct rb_node *node)
{
struct something *foo;
va = rb_entry_safe(node, struct something, rb_node);
return foo ? foo->subtree_max : 0;
}
compute_subtree_max_size(struct vmap_area *va)
{
return max3(va_size(va),
get_subtree_max_size(va->rb_node.rb_left),
get_subtree_max_size(va->rb_node.rb_right));
}
<snip>
What do you think about that?
Thank you.
--
Vlad Rezki
next prev parent reply other threads:[~2019-07-31 14:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-03 4:01 [PATCH v3 0/3] make RB_DECLARE_CALLBACKS more generic Michel Lespinasse
2019-07-03 4:01 ` [PATCH v3 1/3] augmented rbtree: add comments for RB_DECLARE_CALLBACKS macro Michel Lespinasse
2019-07-03 4:01 ` [PATCH v3 2/3] augmented rbtree: add new RB_DECLARE_CALLBACKS_MAX macro Michel Lespinasse
2019-07-08 12:24 ` Michel Lespinasse
2019-07-27 1:44 ` Andrew Morton
2019-07-27 2:20 ` Michel Lespinasse
2019-07-29 10:14 ` Uladzislau Rezki
2019-07-30 7:31 ` Michel Lespinasse
2019-07-31 14:20 ` Uladzislau Rezki [this message]
2019-07-29 10:02 ` Uladzislau Rezki
2019-07-03 4:01 ` [PATCH v3 3/3] augmented rbtree: rework the RB_DECLARE_CALLBACKS macro definition Michel Lespinasse
2019-07-03 7:22 ` [PATCH v3 0/3] make RB_DECLARE_CALLBACKS more generic Peter Zijlstra
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