From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:38065)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <serge.fdrv@gmail.com>) id 1b76oe-0006om-Ne
	for qemu-devel@nongnu.org; Sun, 29 May 2016 15:56:05 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <serge.fdrv@gmail.com>) id 1b76oa-0000k2-JA
	for qemu-devel@nongnu.org; Sun, 29 May 2016 15:56:03 -0400
Received: from mail-lf0-x242.google.com ([2a00:1450:4010:c07::242]:36530)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <serge.fdrv@gmail.com>) id 1b76oa-0000jy-4z
	for qemu-devel@nongnu.org; Sun, 29 May 2016 15:56:00 -0400
Received: by mail-lf0-x242.google.com with SMTP id h68so5402041lfh.3
	for <qemu-devel@nongnu.org>; Sun, 29 May 2016 12:55:59 -0700 (PDT)
From: Sergey Fedorov <serge.fdrv@gmail.com>
References: <1464138802-23503-1-git-send-email-cota@braap.org>
	<1464138802-23503-11-git-send-email-cota@braap.org>
	<574B487B.5080200@gmail.com>
Message-ID: <574B494D.2080602@gmail.com>
Date: Sun, 29 May 2016 22:55:57 +0300
MIME-Version: 1.0
In-Reply-To: <574B487B.5080200@gmail.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH v6 10/15] qht: QEMU's fast,
 resizable and scalable Hash Table
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel/>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Emilio G. Cota" <cota@braap.org>, QEMU Developers <qemu-devel@nongnu.org>, MTTCG Devel <mttcg@listserver.greensocs.com>
Cc: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On 29/05/16 22:52, Sergey Fedorov wrote:
> On 25/05/16 04:13, Emilio G. Cota wrote:
>> +
>> +/* call with head->lock held */
>> +static bool qht_insert__locked(struct qht *ht, struct qht_map *map,
>> +                               struct qht_bucket *head, void *p, uint32_t hash,
>> +                               bool *needs_resize)
>> +{
>> +    struct qht_bucket *b = head;
>> +    struct qht_bucket *prev = NULL;
>> +    struct qht_bucket *new = NULL;
>> +    int i;
>> +
>> +    for (;;) {
>> +        if (b == NULL) {
>> +            b = qemu_memalign(QHT_BUCKET_ALIGN, sizeof(*b));
>> +            memset(b, 0, sizeof(*b));
>> +            new = b;
>> +            atomic_inc(&map->n_added_buckets);
>> +            if (unlikely(qht_map_needs_resize(map)) && needs_resize) {
>> +                *needs_resize = true;
>> +            }
>> +        }
>> +        for (i = 0; i < QHT_BUCKET_ENTRIES; i++) {
>> +            if (b->pointers[i]) {
>> +                if (unlikely(b->pointers[i] == p)) {
>> +                    return false;
>> +                }
>> +                continue;
>> +            }
>> +            /* found an empty key: acquire the seqlock and write */
>> +            seqlock_write_begin(&head->sequence);
>> +            if (new) {
>> +                atomic_rcu_set(&prev->next, b);
>> +            }
>> +            b->hashes[i] = hash;
>> +            atomic_set(&b->pointers[i], p);
>> +            seqlock_write_end(&head->sequence);
>> +            return true;
>> +        }
>> +        prev = b;
>> +        b = b->next;
>> +    }
>> +}
> Here is my attempt:

static bool qht_insert__locked(struct qht *ht, struct qht_map *map,
                               struct qht_bucket *head, void *p,
uint32_t hash,
                               bool *needs_resize)
{
    struct qht_bucket **bpp = &head, *new;
    int i = 0;

    do {
        while (i < QHT_BUCKET_ENTRIES) {
            if ((*bpp)->pointers[i]) {
                if (unlikely((*bpp)->pointers[i] == p)) {
                    return false;
                }
                i++;
                continue;
            }
            goto found;
        }
        bpp = &(*bpp)->next;
        i = 0;
    } while (*bpp);

    new = qemu_memalign(QHT_BUCKET_ALIGN, sizeof(*new));
    memset(new, 0, sizeof(*new));
    atomic_rcu_set(bpp, new);
    atomic_inc(&map->n_added_buckets);
    if (unlikely(qht_map_needs_resize(map)) && needs_resize) {
        *needs_resize = true;
    }
found:
    /* found an empty key: acquire the seqlock and write */
    seqlock_write_begin(&head->sequence);
    (*bpp)->hashes[i] = hash;
    atomic_set(&(*bpp)->pointers[i], p);
    seqlock_write_end(&head->sequence);
    return true;
}

> Feel free to use it as you wish.

Sorry for the chopped email. Hope this one will be better :)

Kind regards,
Sergey