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Clear doorbell bits after masking them before processing.

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In theory this allows to avoid one more expensive doorbell register read
later in some scenarios.  But in practice it also significantly increases
packet rate on PLX hardware, that I can't explain yet, possibly work-
arounding some interrupt delays.

MFC after:	13 days
Sponsored by:	iXsystems, Inc.
This commit is contained in:
Alexander Motin 2017-08-31 21:37:22 +00:00
parent 5ea26aec6e
commit 84f8cfec2f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=323074
1 changed files with 3 additions and 1 deletions
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4
sys/dev/ntb/ntb_transport.c
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@ -1012,8 +1012,10 @@ ntb_transport_doorbell_callback(void *data, uint32_t vector)
vec_mask &= nt->qp_bitmap;
if ((vec_mask & (vec_mask - 1)) != 0)
vec_mask &= ntb_db_read(nt->dev);
if (vec_mask != 0)
if (vec_mask != 0) {
ntb_db_set_mask(nt->dev, vec_mask);
ntb_db_clear(nt->dev, vec_mask);
}
while (vec_mask != 0) {
qp_num = ffsll(vec_mask) - 1;